Optical uses of diamondoid-containing materials

ABSTRACT

Novel optical devices based on diamondoid-containing materials are disclosed. Materials that may be fabricated from diamondoids included diamondoid nucleated CVD films, diamondoid-containing CVD films, molecular crystals, and polymerized materials. Devices that may be fabricated from the diamondoid-containing materials disclosed herein include solid state dye lasers, semiconductor lasers, light emitting diodes, photodetectors, photoresistors, phototransistors, photovoltaic cells, solar cells, anti-reflection coatings, lenses, mirrors, pressure windows, optical waveguides, and particle and radiation detectors.

REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/621,956, filed Jul. 16, 2003, which claims the benefit of U.S.Provisional Patent application No. 60/431,273 filed Dec. 6, 2002, bothapplications of which are hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention are directed in general toward theoptical uses of diamondoid-containing materials. Specifically, thesedevices may include solid state dye lasers, semiconductor lasers, lightemitting diodes, photodetectors, photoresistors, phototransistors,photovoltaic cells, solar cells, anti-reflection coatings, lenses,mirrors, pressure windows, optical waveguides, and particle andradiation detectors.

2. State of the Art

Carbon-containing materials offer a variety of potential uses in opticsand optoelectronics. Elemental carbon has the electronic structure1s²2s²2p², where the outer shell 2s and 2p electrons have the ability tohybridize according to two different schemes. The so-called sp³hybridization comprises four identical δ bonds arranged in a tetrahedralmanner. The so-called sp²-hybridization comprises three trigonal (aswell as planar) a bonds with an unhybridized p-electron occupying a πorbital in a bond oriented perpendicular to the plane of the δ bonds. Atthe “extremes” of crystalline morphology are diamond and graphite. Indiamond, the carbon atoms are tetrahedrally bonded withsp³-hybridization. Graphite comprises planar “sheets” of sp²-hybridizedatoms, where the sheets interact weakly through perpendicularly orientedπ bonds. Carbon exists in other morphologies as well, includingamorphous forms called “diamond-like carbon” (DLC), and the highlysymmetrical spherical and rod-shaped structures called “fullerenes” and“nanotubes,” respectively.

Diamond is an exceptional material because it scores highest (or lowest,depending on one's point of view) in a number of different categories ofproperties. Not only is it the hardest material known, but it has thehighest thermal conductivity of any material at room temperature. Itdisplays superb optical transparency from the infrared through theultraviolet, has the highest refractive index of any clear material, andis an excellent electrical insulator because of its very wide bandgap.It also displays high electrical breakdown strength, and very highelectron and hole mobilities.

A form of carbon not discussed extensively in the literature is the“diamondoid.” Diamondoids are bridged-ring cycloalkanes that compriseadamantane, diamantane, triamantane, and the tetramers, pentamers,hexamers, heptamers, octamers, nonamers, decamers, etc., of adamantane(tricyclo[3.3.1.1^(3,7)] decane), adamantane having the stoichiometricformula C₁₀H₁₆, in which various adamantane units are face-fused to formlarger structures. These adamantane units are essentially subunits ofdiamondoids. The compounds have a “diamondoid” topology in that theircarbon atom arrangements are superimposable on a fragment of an FCC(face centered cubic) diamond lattice. According to embodiments of thepresent invention, electron donating and withdrawing heteroatoms may beinserted into the diamond lattice, thereby creating an n and p-type(respectively) material. The heteroatom is essentially an impurity atomthat has been “folded into” the diamond lattice, and thus many of thedisadvantages of the prior art methods have been avoided.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed toward an opticaldevice comprising a diamondoid-containing material.

One such device is a solid state dye laser comprising adiamondoid-containing lasing medium, an optical pumping system fordelivering energy to the lasing medium, and an optical resonator forprocessing light emitted from the lasing medium.

The solid state dye laser has a lasing medium that may comprise adiamondoid-containing host material and either at least one color centeror an optically active dopant, or both, within the host material. Thecolor center comprises at least one nitrogen heteroatom in aheterodiamondoid positioned adjacent to at least one vacancy or pore.The dopant may be a rare earth element or a transition metal, actinide,lanthanide, or combinations thereof. The dopant may be selected from thegroup consisting of titanium, vanadium, chromium, iron, cobalt, nickel,zinc, zirconium, niobium, cadmium, hafnium, tantalum, tungsten, rhenium,osmium, iridium, platinum, gold, mercury, cerium, praseodymium,neodymium, promethium, samarium, europium, gadolinium, terbium,dysprosium, holmium, erbium, thulium, ytterbium, uranium, andcombinations thereof.

Embodiments of the present invention also include a semiconducting laserhaving a light emitting p-n junction comprising a p-typediamondoid-containing material positioned adjacent to an n-type materialto form a p-n junction for light emission, or a light emitting p-njunction comprising a n-type diamondoid-containing material positionedadjacent to an p-type material to form a p-n junction for lightemission. The semiconducting laser may further include a means forapplying a forward bias across the p-n junction to cause the emission oflaser light from the p-n junction.

Embodiments of the present invention also include a light emitting diodecomprising a diamondoid-containing material having a bandgap, and ameans for generating an electric field to cause at least one electronictransition such that light is emitted from the diode. The electronictransition may occur across the bandgap. The light emitting diode may befurther configured such that the electronic transition occurs withoutparticipation of electronic states within the bandgap.

Embodiments of the present invention also include a photodetectorcomprising a diamondoid-containing material having a bandgap, and ameans of processing current from at least one electronic transition thatresults from the absorption of light by the material. The electronictransition may occur across the bandgap. The photodetector may befurther configured such that the electronic transition occurs withoutparticipation of electronic states within the bandgap.

Additional embodiments include a diamondoid-containing optical deviceselected from the group consisting of a photoresistor, aphototransistor, a photovoltaic cell, and a solar cell. Alsocontemplated as diamondoid-containing optical devices are lenses,mirrors, pressure windows, and optical waveguides.

An antireflection coating according to embodiments of the presentinvention comprises at least one alternating pair of a high refractiveindex diamondoid-containing layer and a low refractive index layer.

Each of the optical devices disclosed herein are fabricated at least inpart from a diamondoid-containing material that is selected from thegroup consisting of a CVD-deposited film, a molecular crystal, and apolymerized film. The material comprises at least one diamondoidselected from the group consisting of adamantane, diamantane, andtriamantane, and heterodiamondoid derivatives thereof. In anotherembodiment, the material comprises at least one diamondoid selected fromthe group consisting of tetramantane, pentamantane, hexamantane,heptamantane, octamantane, nonamantane, decamantane, and undecamantane,and heterodiamondoid derivatives thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview of the embodiments of the present invention,showing the steps of isolating diamondoids from petroleum, synthesizingdiamondoid and heterodiamondoid-containing materials, and creatingoptical and optoelectronic devices from the diamondoid andheterodiamondoid-containing materials;

FIG. 2 shows an exemplary process flow for isolating diamondoids frompetroleum;

FIG. 3 illustrates the relationship of a diamondoid to the diamondcrystal lattice, and enumerates many of the diamondoids available bystoichiometric formula;

FIG. 4 illustrates exemplary heterodiamondoids, and indicates the typesof carbon positions where a heteroatom may be substitutionallypositioned;

FIGS. 5A-B illustrate exemplary pathways for synthetically producingheterodiamondoids;

FIG. 6 illustrates an exemplary processing reactor in which undopeddiamondoid-containing materials, or n and p-type heterodiamondoidmaterials may be made using chemical vapor deposition (CVD) techniques;

FIGS. 7A-C illustrate an exemplary process whereby a heterodiamondoidmay be used to introduce dopant impurity atoms into a growing diamondfilm;

FIGS. 8A-C represent exemplary polymeric materials that may befabricated from diamondoids;

FIG. 8D is an exemplary reaction scheme for the synthesis of a polymerfrom n-type or p-type heterodiamondoids;

FIGS. 9A-N show exemplary linking groups that are electricallyconducting as polymers, and that may be used to link heterodiamondoidsto produce n and p-type materials;

FIG. 10 illustrates an exemplary n or p-type material fabricated fromheterodiamondoids linked by polyaniline oligomers;

FIG. 11 is an stereogram illustrating how an exemplary diamondoid,[1(2,3)4] pentamantane, packs to form a molecular crystal;

FIG. 12 shows how individual heterodiamondoids may be coupled to form ann or p-type device at the molecular level;

FIGS. 13 A, B are energy vs. momentum diagram for a direct bandgapsemiconductor, and an indirect bandgap semiconductor, respectively;

FIG. 13C is an energy vs. momentum diagram for a indirect bandgapsemiconductor having a nanocrystalline or quantum level morphology;

FIG. 14A is a flow chart defining the terminology used to describenitrogen heteroatoms in diamond (from I. Kiflawi et al. in “Theory ofaggregation of nitrogen in diamond,” Properties, Growth and Applicationsof Diamond, edited by M. H. Nazaré and A. J. Neves (Inspec, London,2001), pp. 130-133);

FIG. 14B shows various configurations of nitrogen heteroatoms andvacancies in diamond that lead to lasing color centers (from R. Jones etal. in “Theory of aggregation of nitrogen in diamond” in Properties,Growth and Applications of Diamond, edited by M. H. Nazaré and A. J.Neves (Inspec, London, 2001), pp. 127-129);

FIGS. 15A, B are exemplary diamondoid-containing materials havingnitrogen-vacancy color centers;

FIG. 16 is an exemplary laser having a diamondoid-containing lasingmedium;

FIGS. 17A, B are exemplary diamondoid-containing materials having adopant atom that is responsible for the lasing action;

FIG. 18 is a schematic of an exemplary diamondoid-containing lightemitting diode (LED);

FIG. 19A is a schematic of an exemplary semiconductor laser (laserdiode);

FIGS. 19B, C are bandgap diagrams of an exemplary p-n junction suitablefor use in the semiconductor laser of FIG. 19A;

FIG. 20A, B are schematic diagrams of exemplary diamondoid-containingparticle detectors; and

FIGS. 21A, B are exemplary diamondoid-containing antireflectioncoatings.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure will be organized in the following manner: first,the term diamondoids and heterodiamondoids will be defined, including adiscussion of how these materials may be isolated. Next, the diamondoidcontaining materials that are contemplated to have optical uses will bediscussed. These materials include CVD-deposited diamondoid-containingmaterials, molecular crystals, and polymeric materials. Following adiscussion of diamondoid materials, the optical uses ofdiamondoid-containing materials will be reviewed. These uses includepassive devices, meaning those that are not light emitting, versusactive devices, which may emit light. Passive devices may also includelenses, pressure windows, optical waveguides, and antireflectioncoatings. Active devices include optoelectric devices such asphotoresistors, photodiodes, and phototransistors, light emittingdiodes, and lasers comprising crystalline dye lasers and semiconductinglasers (e.g., laser diodes).

DEFINITION OF DIAMONDOIDS

The term “diamondoids” refers to substituted and unsubstituted cagedcompounds of the adamantane series including adamantane, diamantane,triamantane, tetramantane, pentamantane, hexamantane, heptamantane,octamantane, nonamantane, decamantane, undecamantane, and the like,including all isomers and stereoisomers thereof. The compounds have a“diamondoid” topology, which means their carbon atom arrangement issuperimposable on a fragment of an FCC diamond lattice. Substituteddiamondoids comprise from 1 to 10 and preferably 1 to 4independently-selected alkyl substituents.

Adamantane chemistry has been reviewed by Fort, Jr. et al. in“Adamantane: Consequences of the Diamondoid Structure,” Chem. Rev. vol.64, pp. 277-300 (1964). Adamantane is the smallest member of thediamondoid series and may be thought of as a single cage crystallinesubunit. Diamantane contains two subunits, triamantane three,tetramantane four, and so on. While there is only one isomeric form ofadamantane, diamantane, and triamantane, there are four differentisomers of tetramantane (two of which represent an enantiomeric pair),i.e., four different possible ways of arranging the four adamantanesubunits. The number of possible isomers increases non-linearly witheach higher member of the diamondoid series, pentamantane, hexamantane,heptamantane, octamantane, nonamantane, decamantane, etc.

Adamantane, which is commercially available, has been studiedextensively. The studies have been directed toward a number of areas,such as thermodynamic stability, functionalization, and the propertiesof adamantane-containing materials. For instance, the following patentsdiscuss materials comprising adamantane subunits: U.S. Pat. No.3,457,318 teaches the preparation of polymers from alkenyl adamantanes;U.S. Pat. No. 3,832,332 teaches a polyamide polymer forms fromalkyladamantane diamine; U.S. Pat. No. 5,017,734 discusses the formationof thermally stable resins from adamantane derivatives; and U.S. Pat.No. 6,235,851 reports the synthesis and polymerization of a variety ofadamantane derivatives.

In contrast, the diamondoids tetramantane and higher have receivedcomparatively little attention in the scientific literature. McKervay etal. have reported the synthesis of anti-tetramantane in low yields usinga laborious, multistep process in “Synthetic Approaches to LargeDiamondoid Hydrocarbons,” Tetrahedron, vol. 36, pp. 971-992 (1980). Tothe inventors' knowledge, this is the only higher diamondoid that hasbeen synthesized to date. Lin et al. have suggested the existence of,but did not isolate, tetramantane, pentamantane, and hexamantane in deeppetroleum reservoirs in light of mass spectroscopic studies, reported in“Natural Occurrence of Tetramantane (C₂₂H₂₈), Pentamantane (C₂₆H₃₂) andHexamantane (C₃₀H₃₆) in a Deep Petroleum Reservoir,” Fuel, vol. 74(10),pp. 1512-1521 (1995). The possible presence of tetramantane andpentamantane in pot material after a distillation of adiamondoid-containing feedstock has been discussed by Chen et al. inU.S. Pat. No. 5,414,189.

The four tetramantane structures are iso-tetramantane [1(2)₃],anti-tetramantane [121] and two enantiomers of skew-tetramantane [123],with the bracketed nomenclature for these diamondoids in accordance witha convention established by Balaban et al. in “Systematic Classificationand Nomenclature of Diamond Hydrocarbons-I,” Tetrahedron vol. 34, pp.3599-3606 (1978). All four tetramantanes have the formula C₂₂H₂₈(molecular weight 292). There are ten possible pentamantanes, ninehaving the molecular formula C₂₆H₃₂ (molecular weight 344) and amongthese nine, there are three pairs of enantiomers represented generallyby [12(1)3], [1234], [1213] with the nine enantiomeric pentamantanesrepresented by [12(3)4], [1(2,3)4], [1212]. There also exists apentamantane [1231] represented by the molecular formula C₂₅H₃₀(molecular weight 330).

Hexamantanes exist in thirty nine possible structures with twenty eighthaving the molecular formula C₃₀H₃₆ (molecular weight 396) and of these,six are symmetrical; ten hexamantanes have the molecular formula C₂₉H₃₄(molecular weight 382) and the remaining hexamantane [12312] has themolecular formula C₂₆H₃₀ (molecular weight 342).

Heptamantanes are postulated to exist in 160 possible structures with 85having the molecular formula C₃₄H₄₀ (molecular weight 448) and of these,seven are achiral, having no enantiomers. Of the remaining heptamantanes67 have the molecular formula C₃₃H₃₈ (molecular weight 434), six havethe molecular formula C₃₂H₃₆ (molecular weight 420) and the remainingtwo have the molecular formula C₃₀H₃₄ (molecular weight 394).

Octamantanes possess eight of the adamantane subunits and exist withfive different molecular weights. Among the octamantanes, 18 have themolecular formula C₃₄H₃₈ (molecular weight 446). Octamantanes also havethe molecular formula C₃₈H₄₄ (molecular weight 500); C₃₇H₄₂ (molecularweight 486); C₃₆H₄₀(molecular weight 472), and C₃₃H₃₆ (molecular weight432).

Nonamantanes exist within six families of different molecular weightshaving the following molecular formulas: C₄₂H₄₈ (molecular weight 552),C₄₁H₄₆ (molecular weight 538), C₄₀H₄₄ (molecular weight 524, C₃₈H₄₂(molecular weight 498), C₃₇H₄₀ (molecular weight 484) and C₃₄H₃₆(molecular weight 444).

Decamantane exists within families of seven different molecular weights.Among the decamantanes, there is a single decamantane having themolecular formula C₃₅H₃₆ (molecular weight 456) which is structurallycompact in relation to the other decamantanes. The other decamantanefamilies have the molecular formulas: C₄₆H₅₂ (molecular weight 604);C₄₅H₅₀ (molecular weight 590); C₄₄H₄₈ (molecular weight 576); C₄₂H₄₆(molecular weight 550); C₄₁H₄₄ (molecular weight 536); andC₃₈H₄₀(molecular weight 496).

Undecamantane exists within families of eight different molecularweights. Among the undecamantanes there are two undecamantanes havingthe molecular formula C₃₉H₄₀(molecular weight 508) which arestructurally compact in relation to the other undecamantanes. The otherundecamantane families have the molecular formulas C₄₁H₄₂ (molecularweight 534); C₄₂H₄₄ (molecular weight 548); C₄₅H₄₈ (molecular weight588); C₄₆H₅₀ (molecular weight 602); C₄₉H₅₂ (molecular weight 628);C₄₉H₅₄ (molecular weight 642); and C₅₀H₅₆ (molecular weight 656).

The term “heterodiamondoid” as used herein refers to a diamondoid thatcontains a heteroatom typically substitionally positioned on a latticesite of the diamond crystal structure. A heteroatom is an atom otherthan carbon, and according to present embodiments may be nitrogen,phosphorus, boron, aluminium, lithium, and arsenic. “Substitutionallypositioned” means that the heteroatom has replaced a carbon host atom inthe diamond lattice. Although most heteroatoms are substitutionallypositioned, they may in some cases be found in interstitial sites aswell. As with diamondoids, a heterodiamondoid may be functionalized orderivatized. In the present disclosure, an n-type or p-type diamondoidtypically refers to a an n-type or p-type heterodiamondoid, but in somecases the n or p-type material may comprise diamondoids with noheteroatom.

FIG. 2 shows a process flow illustrated in schematic form, whereindiamondoids may be extracted from petroleum feedstocks, and FIG. 3enumerates the various diamondoid isomers that are available fromembodiments of the present invention.

Synthesis of Heterodiamondoids

FIG. 4 illustrates exemplary heterodiamondoids, indicating the types ofcarbon positions where a heteroatom may be substitutionally positioned.These positions are labeled C-2 and C-3 in the exemplary diamondoid ofFIG. 4. The term “diamondoid” will herein be used in a general sense toinclude diamondoids both with and without heteroatom substitutions. Asdisclosed above, the heteroatom may be an electron donating element suchas N, P, or As, or a hole donating element such as B or Al.

Next, the actual synthesis of such heterodiamondoids will be discussed.Although some heteroadamantane and heterodiamantane compounds have beensynthesized in the past, and this may suggest a starting point for thesynthesis of heterodiamondoids having more than two or three fusedadamantane subunits, it will be appreciated by those skilled in the artthat the complexity of the individual reactions and overall syntheticpathways increase as the number of adamantane subunits increases. Forexample, it may be necessary to employ protecting groups, or it maybecome more difficult to solubilize the reactants, or the reactionconditions may be vastly different from those that would have been usedfor the analagous reaction with adamantane. Nevertheless, it can beadvantageous to discuss the chemistry underlying heterodiamondoidsynthesis using adamantane or diamantane as a substrate because to theinventors' knowledge these are the only systems for which data has beenavailable, prior to the present application.

Nitrogen hetero-adamantane compounds have been synthesized in the past.For example, in an article by T. Sasaki et al., “Synthesis of adamantanederivatives. 39. Synthesis and acidolysis of 2-azidoadamantanes. Afacile route to 4-azahomoadamant-4-enes,” Heterocycles, Vol. 7, No. 1,p. 315 (1977). These authors reported a synthesis of 1-azidoadamantaneand 3-hydroxy-4-azahomoadamantane from 1-hydroxyadamantane. Theprocedure consisted of a substitution of a hydroxyl group with an azidefunction via the formation of a carbocation, followed by acidolysis ofthe azide product.

In a related synthetic pathway, Sasaki et al. were able to subject anadamantanone to the conditions of a Schmidt reaction, producing a4-keto-3-azahomoadamantane as a rearranged product. For detailspertaining to the Schmidt reaction, see T. Sasaki et al., “Synthesis ofAdamantane Derivatives. XII. The Schmidt Reaction of Adamantane-2-one,”J. Org. Chem., Vol. 35, No. 12, p. 4109 (1970).

Alternatively, an 1-hydroxy-2-azaadamantane may be synthesized from1,3-dibromoadamantane, as reported by A. Gagneux et al. in“1-Substituted 2-heteroadamantanes,” Tetrahedron Letters No. 17, pp.1365-1368 (1969). This was a multiple-step process, wherein first thedi-bromo starting material was heated to a methyl ketone, whichsubsequently underwent ozonization to a diketone. The diketone washeated with four equivalents of hydroxylamine to produce a 1:1 mixtureof cis and trans-dioximes; this mixture was hydrogenated to the compoundI-amino-2-azaadamantane dihydrochloride. Finally, nitrous acidtransformed the dihydrochloride to the hetero-adamantane1-hydroxy-2-azadamantane.

Alternatively, a 2-azaadamantane compound may be synthesized from abicyclo[3.3.1]nonane-3,7-dione, as reported by J. G. Henkel and W. C.Faith, in “Neighboring group effects in the P-halo amines. Synthesis andsolvolytic reactivity of the anti-4-substituted 2-azaadamantyl system,”in J. Org. Chem. Vol. 46, No. 24, pp. 4953-4959 (1981). The dione may beconverted by reductive amination (although the use of ammonium acetateand sodium cyanoborohydride produced better yields) to an intermediate,which may be converted to another intermediate using thionyl chloride.Dehalogenation of this second intermediate to 2-azaadamantane wasaccomplished in good yield using LiAlH₄ in DME.

A synthetic pathway that is related in principal to one used in thepresent invention was reported by S. Eguchi et al. in “A novel route tothe 2-aza-adamantyl system via photochemical ring contraction of epoxy4-azahomoadamantanes,” J. Chem. Soc. Chem. Commun., p. 1147 (1984). Inthis approach, a 2-hydroxyadamantane was reacted with a NaN₃ basedreagent system to form the azahomoadamantane, with was then oxidized bym-chloroperbenzoid acid (m-CPBA) to give an epoxy 4-azahomoadamantane.The epoxy was then irradiated in a photochemical ring contractionreaction to yield the N-acyl-2-aza-adamantane.

An exemplary reaction pathway for synthesizing a nitrogen containinghetero iso-tetramantane is illustrated in FIG. 5A. It will be known tothose of ordinary skill in the art that the reactions conditions of thepathway depicted in FIG. 5A will be substantially different from thoseof Eguchi due to the differences in size, solubility, and reactivitiesof tetramantane in relation to adamantane. A second pathway availablefor synthesizing nitrogen containing heterodiamondoids is illustrated inFIG. 5B.

In another embodiment of the present invention, a phosphorus containingheterodiamondoid may be synthesized by adapting the pathway outlined byJ. J. Meeuwissen et. al in “Synthesis of 1-phosphaadamantane,”Tetrahedron Vol. 39, No. 24, pp. 4225-4228 (1983). It is contemplatedthat such a pathway may be able to synthesis heterodiamondoids thatcontain both nitrogen and phosphorus atoms substitutionally positionedin the diamondoid structure, with the advantages of having two differenttypes of electron donating heteroatoms in the same structure.

After preparing heterodiamondoids from diamondoids having no impurityatoms, the resulting heterodiamondoids may be fabricated into bulkmaterials for use in semiconductor devices. Alternatively, it iscontemplated that the heterodiamondoids may be used at a molecularlevel, where bulk materials are not necessary. The preparation of thesematerials will be discussed next, and they are also discussed in acopending application titled “Heterodiamondoids,” by S. Liu, J. E. Daho,and R. M. Carlson, assigned to the assignee of the present application,and incorporated herein in its entirety.

Isolation of Diamondoids from Petroleum Feedstocks

Feedstocks that contain recoverable amounts of higher diamondoidsinclude, for example, natural gas condensates and refinery streamsresulting from cracking, distillation, coking processes, and the like.Particularly preferred feedstocks originate from the Norphlet Formationin the Gulf of Mexico and the LeDuc Formation in Canada.

These feedstocks contain large proportions of lower diamondoids (oftenas much as about two thirds) and lower but significant amounts of higherdiamondoids (often as much as about 0.3 to 0.5 percent by weight). Theprocessing of such feedstocks to remove non-diamondoids and to separatehigher and lower diamondoids (if desired) can be carried out using, byway of example only, size separation techniques such as membranes,molecular sieves, etc., evaporation and thermal separators either undernormal or reduced pressures, extractors, electrostatic separators,crystallization, chromatography, well head separators, and the like.

A preferred separation method typically includes distillation of thefeedstock. This can remove low-boiling, non-diamondoid components. Itcan also remove or separate out lower and higher diamondoid componentshaving a boiling point less than that of the higher diamondoid(s)selected for isolation. In either instance, the lower cuts will beenriched in lower diamondoids and low boiling point non-diamondoidmaterials. Distillation can be operated to provide several cuts in thetemperature range of interest to provide the initial isolation of theidentified higher diamondoid. The cuts, which are enriched in higherdiamondoids or the diamondoid of interest, are retained and may requirefurther purification. Other methods for the removal of contaminants andfurther purification of an enriched diamondoid fraction can additionallyinclude the following nonlimiting examples: size separation techniques,evaporation either under normal or reduced pressure, sublimation,crystallization, chromatography, well head separators, flashdistillation, fixed and fluid bed reactors, reduced pressure, and thelike.

The removal of non-diamondoids may also include a thermal treatment stepeither prior or subsequent to distillation. The thermal treatment stepmay include a hydrotreating step, a hydrocracking step, ahydroprocessing step, or a pyrolysis step. Thermal treatment is aneffective method to remove hydrocarbonaceous, non-diamondoid componentsfrom the feedstock, and one embodiment of it, pyrolysis, is effected byheating the feedstock under vacuum conditions, or in an inertatmosphere, to a temperature of at least about 390° C., and mostpreferably to a temperature in the range of about 410 to 450° C.Pyrolysis is continued for a sufficient length of time, and at asufficiently high temperature, to thermally degrade at least about 10percent by weight of the non-diamondoid components that were in the feedmaterial prior to pyrolysis. More preferably at least about 50 percentby weight, and even more preferably at least 90 percent by weight of thenon-diamondoids are thermally degraded.

While pyrolysis is preferred in one embodiment, it is not alwaysnecessary to facilitate the recovery, isolation or purification ofdiamondoids. Other separation methods may allow for the concentration ofdiamondoids to be sufficiently high given certain feedstocks such thatdirect purification methods such as chromatography including preparativegas chromatography and high performance liquid chromatography,crystallization, fractional sublimation may be used to isolatediamondoids.

Even after distillation or pyrolysis/distillation, further purificationof the material may be desired to provide selected diamondoids for usein the compositions employed in this invention. Such purificationtechniques include chromatography, crystallization, thermal diffusiontechniques, zone refining, progressive recrystallization, sizeseparation, and the like. For instance, in one process, the recoveredfeedstock is subjected to the following additional procedures: 1)gravity column chromatography using silver nitrate impregnated silicagel; 2) two-column preparative capillary gas chromatography to isolatediamondoids; 3) crystallization to provide crystals of the highlyconcentrated diamondoids.

An alternative process is to use single or multiple column liquidchromatography, including high performance liquid chromatography, toisolate the diamondoids of interest. As above, multiple columns withdifferent selectivities may be used. Further processing using thesemethods allow for more refined separations which can lead to asubstantially pure component.

Detailed methods for processing feedstocks to obtain higher diamondoidcompositions are set forth in U.S. Provisional Patent Application No.60/262,842 filed Jan. 19, 2001; U.S. Provisional Patent Application No.60/300,148 filed Jun. 21, 2001; and U.S. Provisional Patent ApplicationNo. 60/307,063 filed Jul. 20, 2001, and a co-pending application titled“Processes for concentrating higher diamondoids,” by B. Carlson et al.,assigned to the assignee of the present application. These applicationsare herein incorporated by reference in their entirety.

Materials

The diamondoid-containing materials that may be used in embodiments ofthe present invention may be fabricated in a number of different ways.Methods of fabrication include are CVD deposited diamondoid anddiamondoid-containing materials, CVD nucleated diamond materials;polymeric materials including polymerized diamondoids and/ordiamondoid-containing films; and molecular crystals, including thosethat are self assembled or self crystallizing.

In a first embodiment, diamondoids (which may or may not containheteroatoms) are injected into a reactor carrying out a conventional CVDprocess such that the diamondoids are added to and become a part of anextended diamond structure, and if present, the heteroatom becomessubstitutionally positioned on a diamond lattice site. Such a heteroatombehaves like a dopant in conventionally produced doped diamond. Inanother embodiment, heterodiamondoids may be derivatized (orfunctionalized) with functional groups capable of causing a polymerizingreaction, and in one embodiment, the functional groups linking twoadjacent heterodiamondoids are electrically semiconducting. In a thirdembodiment, the n or p-type material comprises only heterodiamondoids ina bulk heterodiamondoid crystal, wherein the individualheterodiamondoids in the crystal are held together by van der Waals(London) forces.

Optical uses of diamondoid-containing materials in accordance with thepresent embodiments are not limited to these types of materials, and mayinclude any other type of film that contains the diamondoid form ofcarbon.

Preparation of Diamondoid-Containing Materials Using CVD Techniques

In a first embodiment, diamondoid-containing materials, including n andp-type diamondoid materials, are fabricated according to embodiments ofthe present invention using chemical vapor deposition (CVD) techniques.Diamondoids may be employed as carbon precursor and heterodiamondoids asself-contained dopant sources already sp³-hybridized in a diamondlattice, using conventional CVD techniques. In a novel approach, the useof the diamondoids and heterodiamondoids may be used to nucleate adiamond film using conventional CVD techniques, where such conventionaltechniques include thermal CVD, laser CVD, plasma-enhanced orplasma-assisted CVD, electron beam CVD, and the like.

Conventional methods of synthesizing diamond by plasma enhanced chemicalvapor deposition (PECVD) techniques are well known in the art, and dateback to around the early 1980's. Although it is not necessary to discussthe specifics of these methods as they relate to the present invention,one point in particular that should be made since it is relevant to therole hydrogen plays in the synthesis of diamond by “conventional”plasma-CVD techniques.

In one method of synthesizing diamond films discussed by A. Erdemir etal. in “Tribology of Diamond, Diamond-Like Carbon, and Related Films,”in Modern Tribology Handbook, Vol. Two, B. Bhushan, Ed. (CRC Press, BocaRaton, 2001) pp. 871-908, a modified microwave CVD reactor is used todeposit a nanocrystalline diamond film using a C₆₀ fullerene, ormethane, gas carbon precursor. To introduce the C₆₀ fullerene precursorinto the reactor, a device called a “quartz transpirator” is attached tothe reactor, wherein this device essentially heats a fullerene-rich sootto temperatures between about 550 and 600° C. to sublime the C₆₀fullerene into the gas phase.

It is contemplated that a similar device may be used to sublimediamondoids into the gas phase such that they may be introduced to a CVDreactor. An exemplary reactor is shown in generally at 600 in FIG. 6. Areactor 600 comprises reactor walls 601 enclosing a process space 602. Agas inlet tube 603 is used to introduce process gas into the processspace 602, the process gas comprising methane, hydrogen, and optionallyan inert gas such as argon. A diamondoid subliming or volatilizingdevice 604, similar to the quartz transpirator discussed above, may beused to volatilize and inject a diamondoid containing gas into thereactor 600. The volatilizer 604 may include a means for introducing acarrier gas such as hydrogen, nitrogen, argon, or an inert gas such as anoble gas other than argon, and it may contain other carbon precursorgases such as methane, ethane, or ethylene.

Consistent with conventional CVD reactors, the reactor 600 may haveexhaust outlets 605 for removing process gases from the process space602; an energy source 606 for coupling energy into process space 602(and striking a plasma from) process gases contained within processspace 602; a filament 607 for converting molecular hydrogen tomonoatomic hydrogen; a susceptor 608 onto which a diamondoid containingfilm 609 is grown; a means 610 for rotating the susceptor 608 forenhancing the sp³-hybridized uniformity of the diamondoid-containingfilm 609; and a control system 611 for regulating and controlling theflow of gases through inlet 603; the amount of power coupled from source606 into the processing space 602; the amount of diamondoids injectedinto the processing space 602; the amount of process gases exhaustedthrough exhaust ports 605; the atomization of hydrogen from filament607; and the means 610 for rotating the susceptor 608. In an exemplaryembodiment, the plasma energy source 606 comprises an induction coilsuch that power is coupled into process gases within processing space602 to create a plasma 612.

A diamondoid and/or heterodiamondoid precursor may be injected intoreactor 600 according to embodiments of the present invention throughthe volatilizer 604, which serves to volatilize the diamondoids. Acarrier gas such as methane or argon may be used to facilitate transferof the diamondoids entrained in the carrier gas into the process space602. The injection of such heterodiamondoids provides a method wherebyimpurity atoms may be inserted into a diamond film without having toresort to crystal damaging techniques such as ion implantation.

It is contemplated in some embodiments that the injected methane gasprovides the majority of the carbon material present in a CVD createdfilm, with the diamondoid portion of the input gas facilitating the rateof growth, but more importantly, the heteroatom of the heterodiamondoidsupplying the impurity that will eventually function as the electrondonor or acceptor in the n and p-type diamond or diamondoid-containingfilm. This process is illustrated schematically in FIGS. 7A-7C.

Referring to FIG. 7A, a substrate 700 is positioned within the CVDreactor 600, and a conventional CVD diamond film 701 is grown on thesubstrate 700. This diamond film 701 comprises tetrahedrally bondedcarbon atoms, where a carbon atom is represented by the intersection oftwo lines in FIG. 7A-C, such as depicted by reference numeral 702, and ahydrogen terminated surface represented by the end of a line, as shownby reference numeral 703. The hydrogen passivated surface 703 of thediamond film 701 is very important. Hydrogen participates in thesynthesis of diamond by PECVD techniques by stabilizing the sp³ bondcharacter of the growing diamond surface. As discussed in the referencecited above, A. Erdemir et al. teach that hydrogen also controls thesize of the initial nuclei, dissolution of carbon and generation ofcondensable carbon radicals in the gas phase, abstraction of hydrogenfrom hydrocarbons attached to the surface of the growing diamond film,production of vacant sites where sp³ bonded carbon precursors may beinserted. Hydrogen etches most of the double or sp² bonded carbon fromthe surface of the growing diamond film, and thus hinders the formationof graphitic and/or amorphous carbon. Hydrogen also etches away smallerdiamond grains and suppresses nucleation. Consequently, CVD growndiamond films with sufficient hydrogen present leads to diamond coatingshaving primarily large grains with highly faceted surfaces.

Referring again to FIG. 7A, a heterodiamondoid 704 is injected in thegas phase into the CVD reactor via the volatilizing device 604 describedabove. Schematically, the heterodiamondoid 704 has tetrahedrally bondedcarbon atoms at the intersections of lines 702, as well as a hydrogenpassivated surface at the end of the lines 703, as before. Theheterodiamondoid 704 also has a heteroatom 705 substitutionallypositioned within its lattice structure, and the heteroatom may be anelectron donor or acceptor.

During the deposition process, the heterodiamondoid 704 is deposited onthe surface of the CVD diamond film 701, as shown in FIG. 7B. The carbonatoms of the heterodiamondoid 704 become tetrahedrally coordinated with(bonded to) the carbon atoms of the film 701 to produce a continuousdiamond lattice structure across the newly created interface of theheterodiamondoid 704 and the diamond film 701.

The result is a diamond film 707 having an impurity atom (which may bean electron donor or acceptor) substitutionally positioned on a latticesite position within the diamond crystal structure, as shown in FIG. 7C.Since the heterodiamondoid has been incorporated into the growingdiamond film, so has its heteroatom become incorporated into the growingfilm, and the heteroatom has retained its sp³-hybridizationcharacteristics through the deposition process. Advantages of thepresent embodiment include the insertion of an impurity atom into thediamond lattice without having to resort to crystal damagingimplantation techniques.

The weight of heterodiamondoids and substituted heterodiamondoids, as afunction of the total weight of the CVD film (where the weight of theheterodiamondoid functional groups are included in the heterodiamondoidportion), may in one embodiment range from about 1 part per million(ppm) to 100 percent by weight. Alternatively, the content ofdiamondoids and heterodiamondoids, and derivatives thereof may rangefrom about 1 part per million to 95 percent by weight. In anotherembodiment, the content of heterodiamondoids and substitutedheterodiamondoids is about 10 ppm to 1 percent by weight. In anotherembodiment, the proportion of heterodiamondoids and substitutedheterodiamondoids in the CVD film relative to the total weight of thefilm is about 100 ppm to 0.01 percent by weight.

Preparation of Diamondoid-Containing Materials Using PolymerizationTechniques

In an alternative embodiment, diamondoid-containing films or materialsmay be fabricated by polymerization. For this to occur, it is necessaryto derivatize (or functionalize) the diamondoids prior topolymerization, and methods of forming diamondoid derivatives, andtechniques for polymerizing derivatized diamondoids, are discussed inU.S. patent application Ser. No. 60/334,939, entitled “PolymerizableHigher Diamondoid Derivatives,” by Shenggao Liu, Jeremy E. Dahl, andRobert M. Carlson, filed Dec. 4, 2001, and incorporated herein byreference in its entirety.

To fabricate a polymeric film containing diamondoid constituents, eitheras part of the main polymeric chain, or as side groups or branches offof the main chain, one first synthesizes a derivatized diamondoidmolecule, that is to say, a diamondoid having at least one functionalgroup substituting one of the original hydrogens. As discussed in thatapplication, there are two major reaction sequences that may be used toderivatize heterodiamondoids: nucleophilic (S_(N)1-type) andelectrophilic (S_(E)2-type) substitution reactions.

S_(N)1-type reactions involve the generation of diamondoid carbocations,which subsequently react with various nucleophiles. Since tertiary(bridgehead) carbons of diamondoids are considerably more reactive thansecondary carbons under S_(N)1 reaction conditions, substitution at atertiary carbon is favored.

S_(E)2-type reactions involve an electrophilic substitution of a C—Hbond via a five-coordinate carbocation intermediate. Of the two majorreaction pathways that may be used for the functionalization ofheterodiamondoids, the S_(N)1-type may be more widely utilized forgenerating a variety of heterodiamondoid derivatives. Mono andmulti-brominated heterodiamondoids are some of the most versatileintermediates for functionalizing heterodiamondoids. These intermediatesare used in, for example, the Koch-Haaf, Ritter, and Friedel-Craftsalkylation and arylation reactions. Although direct bromination ofheterodiamondoids is favored at bridgehead (tertiary) carbons,brominated derivatives may be substituted at secondary carbons as well.For the latter case, when synthesis is generally desired at secondarycarbons, a free radical scheme is often employed.

Although the reaction pathways described above may be preferred in someembodiments of the present invention, many other reaction pathways maycertainly be used as well to functionalize a heterodiamondoid. Thesereaction sequences may be used to produce derivatized heterodiamondoidshaving a variety of functional groups, such that the derivatives mayinclude heterodiamondoids that are halogenated with elements other thanbromine, such as fluorine, alkylated diamondoids, nitrated diamondoids,hydroxylated diamondoids, carboxylated diamondoids, ethenylateddiamondoids, and aminated diamondoids. See Table 2 of the co-pendingapplication “Polymerizable Higher Diamondoid Derivatives” for a listingof exemplary substituents that may be attached to heterodiamondoids.

Diamondoids and heterodiamondoids, as well as derivatived forms thereofhaving substituents capable of entering into polymerizable reactions,may be subjected to suitable reaction conditions such that polymers areproduced. The polymers may be homopolymers or heteropolymers, and thepolymerizable diamondoid and/or heterodiamondoid derivatives may beco-polymerized with nondiamondoid, diamondoid, and/orheterodiamondoid-containing monomers. Polymerization is typicallycarried out using one of the following methods: free radicalpolymerization, cationic, or anionic polymerization, andpolycondensation. Procedures for inducing free radical, cationic,anionic polymerizations, and polycondensation reactions are well knownin the art.

Free radical polymerization may occur spontaneously upon the absorptionof an adequate amount of heat, ultraviolet light, or high-energyradiation. Typically, however, this polymerization process is enhancedby small amounts of a free radical initiator, such as peroxides, azacompounds, Lewis acids, and organometallic reagents. Free radicalpolymerization may use either non-derivatized or derivatizedheterodiamondoid monomers. As a result of the polymerization reaction acovalent bond is formed between diamondoid, nondiamondoid, andheterodiamondoid monomers such that the diamondoid or heterodiamondoidbecomes part of the main chain of the polymer. In another embodiment,the functional groups comprising substituents on a diamondoid orheterodiamondoid may polymerize such that the diamondoids orheterodiamondoids end up being attached to the main chain as sidegroups. Diamondoids and heterodiamondoids having more than onefunctional group are capable of cross-linking polymeric chains together.

For cationic polymerization, a cationic catalyst may be used to promotethe reaction. Suitable catalysts are Lewis acid catalysts, such as borontrifluoride and aluminum trichloride. These polymerization reactions areusually conducted in solution at low-temperature.

In anionic polymerizations, the derivatized diamondoid orheterodiamdondoid monomers are typically subjected to a strongnucleophilic agent. Such nucleophiles include, but are not limited to,Grignard reagents and other organometallic compounds. Anionicpolymerizations are often facilitated by the removal of water and oxygenfrom the reaction medium.

Polycondensation reactions occur when the functional group of onediamondoid or heterodiamondoid couples with the functional group ofanother; for example, an amine group of one diamondoid orheterodiamondoid reacting with a carboxylic acid group of another,forming an amide linkage. In other words, one diamondoid orheterodiamondoid may condense with another when the functional group ofthe first is a suitable nucleophile such as an alcohol, amine, or thiolgroup, and the functional group of the second is a suitable electrophilesuch as a carboxylic acid or epoxide group. Examples ofheterodiamondoid-containing polymers that may be formed viapolycondensation reactions include polyesters, polyamides, andpolyethers.

Exemplary diamondoid-containing polymeric films are illustratedschematically in FIGS. 8A-8C. Referring to FIG. 8A, adiamondoid-containing polymer is shown generally at 800, where thepolymer comprises diamondoid monomers 801, 802, 803 linked throughcarbon-to-carbon covalent bonds 804. The diamondoid monomers 801, 802,803 may comprise any member of the higher diamondoid series tetramantanethrough undecamantane. The covalent linkage 804 comprises a bond betweentwo carbon atoms where each of carbon atoms of the bond are members ofthe two adjacent diamondoids. Stated another way, two diamondoids in thepolymeric chain are directly linked such that there are no interveningcarbon atoms that are not part of a diamondoid nucleus (or part of anadamantane subunit).

Alternatively, two adjacent diamondoids may be covalently linked throughcarbon atoms that are not members (part of the carbon nucleus) of eitherof the two diamondoids. Such a covalent linkage is shown schematicallyin FIG. 8A at reference numeral 805. As discussed above, adjacentdiamondoids may be covalently connected through, for example, an esterlinkages 806, an amide linkages 807, and an ether linkage is 808.

In an alternative embodiment, a diamondoid-containing polymer showngenerally at 820 in FIG. 8B comprises a copolymer formed from themonomers ethylene and a higher diamondoid having at least one ethylenesubstituent. The diamondoid monomer shown at 821 contains onesubstituent ethylene group. The diamondoid monomer shown at 822 containstwo ethylene substituents, and could have more than two substituents.Either or both of these diamondoids may be copolymerized with ethylene823 itself, as a third monomer participating in the reaction, to formthe co-polymer 820 or subunits thereof. Because the diamondoid monomer822 has two substituent polymerizable moieties attached to it, thisparticular monomer is capable of cross-linking chains 824 and chain 825together. Such a cross-linking reaction is capable of producing polymershaving properties other than those of the polymer depicted in FIG. 8A,since for the FIG. 8A polymer the diamondoid nuclei are positionedwithin the main chain. A consequence of the structures formed in FIGS.8A and 8B is that it is possible to incorporate metallic elements,particles, and inclusions (illustrated as M1 to M3) by inserting theminto the interstities of folded and cross-linked polymeric chains.Diamondoid-containing materials may be doped in such a manner withalkali metals, alkali earth metals, halogens, rare earth elements, B,Al, Ga, In, Tl, V, Nb, and Ta to improve thermal conductivity and/oroptical properties if desired. The relative ratios of the monofunctionaldiamondoid monomer, the difunctional diamondoid monomer, and theethylene monomer in the exemplary polymer of FIG. 8B may of course beadjusted to produce the desired properties with regard to stiffness,compactness, and ease of processing.

The exemplary polyimide-diamondoid polymer shown generally at 830 inFIG. 8C contains segments of polyimide chains derived fromrepresentative groups selected to illustrate certain relationshipsbetween structure and properties, in particular, how the properties ofthe exemplary polymer relate to the processing it has undergone. Thedianhydride PMDA (pyromellitic dianhydride) shown at 831 and the diaminediaminofluorenone 832 are introduced into the chain for rigidity. Thedianhydride BTDA (benzophenonetetracarboxylic dianhydride) shown at 833provides the capability of further reaction at the carboxyl site,possibly for crosslinking purposes, and/or for the potential inclusionof metallic moieties into the material. The dianhydride oxydiphthalicdianhydride (ODPA) shown at 834, and the diamines oxydianiline (ODA) at835 and bisaminophenoxybenzene at 836 may be introduced for chainflexibility and ease of processing of the material. Additionally,fluorinated dianhydrides such as 6FDA (not shown) may be introduced tolower the overall dielectric constant of the material.

The diamondoid components of the exemplary polymer illustratedschematically in FIG. 8C comprise a pentamantane diamondoid at 866,which is positioned in the main chain of the polymer, and an octamantanediamondoid at 837, which comprises a side group of thediamondoid-polyimide polymer at a position of a diamine (in thisexemplary case, diaminobenzophenone) component. A diamondoid component838 may be used as a cross-linking agent to connect two adjacent chains,through covalent linkages, or diamondoid component 838 may be passivelypresent as an unfunctionalized “space filler” wherein it serves toseparate main polymeric chains simply by steric hindrance. Folding ofthe main polymeric chains, particularly when diamondoid “fillers” 838are present, may create voids 839, which may serve to reduce the overalldielectric constant of the material, since the dielectric constant ofair (if it is the gas within the void), is one.

The diamondoid-containing polymers discussed above may be applied to asubstrate undergoing microelectronic processing by any of methods knownin the art, such as spin coating, molding, extrusion, and vapor phasedeposition. The weight of diamondoids and substituted diamondoids as afunction of the total weight of the polymer (where the weight of thediamondoid functional groups are included in the diamondoid portion) mayin one embodiment range from about 0.001 to 100 percent by weight.

In one embodiment of the present invention, a synthesis technique forthe polymerization of heterodiamondoids comprises a two-step synthesis.The first step involves an oxidation to form at least one ketonefunctionality at a secondary carbon (methylene) position of aheterodiamondoid. The heterodiamondoid may be directly oxidized using areagent such as concentrated sulfuric acid to produce aketo-heterodiamondoid. In other situations, it may be desirable toconvert the hydrocarbon to an alcohol, and then to oxidize the alcoholto the desired ketone. Alternatively, the heterodiamondoid may beinitially halogenated (for example with N-chlorosuccinimide, NCS), andthe resultant halogenated diamondoid reacted with base (for example,KHCO₃ or NaHCO₃, in the presence of dimethyl sulfoxide). It will beunderstood by those skilled in the art that it may be necessary toprotect the heteroatom in the heterodiamondoid prior to the oxidationstep.

The second step consists of the coupling two or moreketo-heterodiamondoids to produce the desired polymer ofheterodiamondoids. It is known in the art to couple diamondoids by aketone chemistry, and one process has been described as the McMurrycoupling process in U.S. Pat. No. 4,225,734. Alternatively, coupling maybe effected by reacting the keto-heterodiamondoids in the presence ofTiCl₃, Na, and 1,4-dioxane. Additionally, polymers of diamondoids(adamantanes) have been illustrated in Canadian Patent Number 2100654.One of ordinary skill in the art will understand that because of thelarge number of oxidation and coupling reaction conditions available, avariety of keto-heterodiamondoids may be prepared with a diversity ofconfigurational, positional, and stereo configurations.

In an alternative embodiment, it is desirable to conduct a sequence ofoxidation/coupling steps to maximize the yield of a heterodiamondoidpolymer. For example, when the desired polymeric heterodiamondoidcontains interposing bridgehead carbons, a three step procedure may beuseful. This procedure comprises chlorinating an intermediate coupledpolymeric heterodiamondoid with a selective reagent such as NCS. Thisproduces a chlorinated derivative with the newly introduced chlorine ona methylene group adjacent to the double bond (or bonds) that werepresent in the intermediate. The chloro-derivative is convertable to thedesired ketone by substitution of the chlorine by a hydroxyl group, andfurther oxidation by a reagent such as sodium bicarbonate indimethylsulfoxide (DMSO). Additional oxidation may be carried out toincrease ketone yields, the additional treatment comprising furthertreatment with pyridine chlorochromate (PCC).

A schematic illustration of a polymerization reaction betweenheterodiamondoid monomers is illustrated in FIG. 8D. A heterodiamondoid870 is oxidized using sulfuric acid to the keto-heterodiamondoid 871.The particular diamondoid shown at 871 is a tetramantane, however, anyof the diamondoids described above are applicable. Again, the symbol “X”represents a heteroatom substitutionally positioned on a lattice site ofthe diamondoid. The ketone group in this instance is attached toposition 872.

Two heterodiamondoids 871 may be coupled using a McMurry reagent asshown in step 872. According to embodiments of the present invention,the coupling between two adjacent heterodiamondoids may be made betweenany two carbons of each respective heterodiamondoid's nuclear structure,and in this exemplary situation the coupling has been made betweencarbons 873 of diamondoid 876 and carbon 874 of heterodiamondoid 876. Itwill be apparent to those skilled in the art that this process may becontinued; for example, the pair of heterodiamondoids shown generally at877 may be functionalized with ketone groups on the heterodiamondoids875 and 876, respectively, to produce the intermediate 878, where twointermediates 878 may couple to form the complex 879. In this manner, apolymer may be constructed using the individual heterodiamondoids 870such that n-type or p-type material is fabricated. Such a material isexpected to be electrically conducting due to the pi-bonding betweenadjacent heterodiamondoid monomers.

In an alternative embodiment, individual heterodiamondoid molecules maybe coupled with electrically conductive polymer “linkers” to generate ann-type or p-type heterodiamondoid material. In this context, a linker isdefined as a short segment of polymer comprising one to ten monomersegments of a larger polymer. The linkers of the present invention maycomprise a conductive polymer such that electrical conductivity isestablished between adjacent heterodiamondoids in the overall bulkmaterial. Polymers with conjugated pi-electron backbones are capable ofdisplaying these electronic properties. Conductive polymers are known,and the technology of these materials have been described in a chaptertitled “Electrically Conductive Polymers” by J. E. Frommer and R. R.Chance in High Performance Polymers and Composites, J. I. Kroschwitx,Ed. (Wiley, New York, 1991), pp. 174 to 219. The conductivity of many ofthese polymers have been described in this chapter, and compared tometals, semiconductors, and insulators. A typical semiconducting polymeris poly(p-phenylene sulfide), which has a conductivity as high as 10³Siemens/cm² (these units are identical to Ω⁻¹cm⁻¹), and as low as 10⁻¹⁵,which is as insulating as nylon. Polyacetylene is more conducting withan upper conductance of 10³Ω⁻¹cm⁻¹, and a lower conductance of about10⁻⁹Ω⁻¹cm⁻¹.

According to embodiments of the present invention, heterodiamondoids maybe electrically connected to form a bulk n or p-type material usingoligomers of the polymers discussed above. In this instance, an oligomerrefers to a polymerization of about 2 to 20 monomers. Thus, an oligomermay be thought of as a short polymer. In this instance, the purpose ofthe oligomers, and/or linkers, is to electrically connect a number ofheterodiamondoids into a three-dimensional structure such that a bulkmaterial having p-type or n-type electrical conductivity may beachieved.

Conductive polymers have been discussed in general by J. E. Frommer andR. R. Chance in a chapter titled “Electrically conductive polymers,” inHigh Performance Polymers and Composites, J. I. Kroschwitz, ed. (Wiley,New York, 1991), pp. 174-219. To synthesize a conventional conductivepolymer, it is important to incorporate moieties having an extendedπ-electron conjugation. The monomers that are typically used tosynthesize such polymers are either aromatic, or contain multiplecarbon-carbon double bonds that are preserved the in the final polymericbackbone. Alternatively, conjugation may be achieved in a subsequentstep that transforms the initial polymer product into a conjugatedpolymer. For example, the polymerization of acetylene yields a productof conjugated ethylene units, whereas a benzene polymerization producesa chain of covalently linked aromatic units.

A catalog of exemplary oligomers (linkers) that may be used to connectheterodiamondoids in an electrically conductive manner are illustratedin FIGS. 9A-N. Typical linkers that have been shown to be electricallyconductive are polyacetylene in FIG. 9A, polythiophene in FIG. 9E, andpolyparaphenylene vinylene in FIG. 9F. An electrically conductive linkerthat will be highlighted as an example in the next discussion ispolyaniline, the oligomer of which has been depicted in FIG. 9N.

A schematic diagram of a heterodiamondoid polymer generated withpolyaniline linking groups is depicted in FIG. 10. The polymer of FIG.10 is only exemplary in that the conductive linker groups betweenadjacent heterodiamondoids is a polyaniline functionality, but of coursethe linking group could be any conductive polymer, many of whichcomprise conductive diene systems. In FIG. 10 a heterodiamondoid 1001 islinked to a heterodiamondoid 1002 via a short segment of polyanilineoligomer 1003. The same applies for the connection 1004 to theheterodiamondoid 1005 within the same linear chain.

The polymer shown generally at 1000 may also contain crosslinks thatconnect a linear chain 1006 with 1007. This creates a three-dimensionalcrosslinked polymer with electrical conductivity in a three-dimensionalsense. Crosslinked chains 1008 may be used to connect adjacent linearchains 1006 and 1007. A three-dimensional matrix of an electricallyconducting diamondoid containing material is thus established. Eachheterodiamondoid 1001 and 1002 contains within its structure aheteroatom which is either an electrical donor or electrical accepter.Overall, fabrication of an n-type or p-type heterodiamondoid material isachieved.

Molecular Crystals

A third method of fabricating diamondoid-containing materials iscrystallize the diamondoids into a solid, where the individualdiamondoids comprising the solid are held together by Van der Waalsforces (also called London or dispersive forces). Molecules that areheld together in such a fashion have been discussed by J. S. Moore andS. Lee in “Crafting Molecular Based Solids,” Chemistry and Industry,July, 1994, pp. 556-559, and are called “molecular solids” in the art.These authors state that in contrast to extended solids or ioniccrystals, the preferred arrangement of molecules in a molecular crystalis presumably one that minimizes total free energy, and thus thefabrication of a molecular crystal is controlled by thermodynamicconsiderations, unlike a synthetic process. An example of a molecularcrystal comprising the pentamantane [1(2,3)4] will be discussed next.

In an exemplary embodiment, a molecular crystal comprising [1(2,3)₄]pentamantane was formed by the chromatographic and crystallographictechniques described above. These aggregations of diamondoids pack toform actual crystals in the sense that a lattice plus a basis may bedefined. In this embodiment, the [1(2,3)₄] pentamantane is found to packin an orthorhombic crystal system having the space group Pnma, with unitcell dimensions a=11.4706, b=12.6418, and c=12.5169 angstroms,respectively. To obtain that diffraction data, a pentamantane crystalwas tested in a Bruker SMART 1000 diffractometer using radiation ofwavelength 0.71073 angstroms, the crystal maintained at a temperature of90 K.

A unit cell of the pentamantane molecular crystal is illustrated in FIG.11. This diagram illustrates the generalized manner in whichheterodiamondoids may pack in order to be useful according toembodiments of the present invention. These molecular crystals displaywell-defined exterior crystal facets, and are transparent to visibleradiation.

Referring to FIG. 11, the packing of the [1(2,3)₄] pentamantane isillustrated in three dimensions by the stereogram having two images1102, 1103, that may be viewed simultaneously. Each unit cell of themolecular crystal contains four pentamantane molecules, where themolecules are arranged such that there is one central cavity or pore1106 per unit cell. In many (if not all) of the embodiments of thepresent invention, the cavity that is created by packing diamondoid orheterodiamondoid molecules into a crystal are the packed pentamantaneunits may be too small to accommodate a transition element metal, butcrystallization around a transition element, such as gold, may occursuch that the conductivity of the material is enhanced. There may benone, or more than one pore in molecular crystals of other diamondoids,and the sizes of these pores may vary.

The significance of the packing of the [1(2,3)4] pentamantanesillustrated in FIG. 11 is that a p or n-type diamondoid material, andjunction fabricated therefrom, may be realized with little furtherprocessing than isolation using chromatographic techniques. In otherwords, no functionalization is necessary to polymerize or link upindividual diamondoid molecules, and no expensive deposition equipmentis needed in this embodiment. Since many of these crystal aremechanically soft and easily compressible, being held together by vander Waals forces, an exterior “mold” is contemplated to support thevarious regions of the device (in essence, for example, a lasing orlight emitting medium may even be “semi-liquid”).

An exemplary subunit of polymerized diamondoids (and/orheterodiamondoids) that are contemplated to be capable of forming amolecular crystal is illustrated in FIG. 12. Referring to FIG. 12individual heterodiamondoids 1201, 1202 that contain nitrogenheteroatoms may be coupled to form dimer of diamondoids 1205; likewise,individual heterodiamondoids 1203, 1204 may be coupled to form a dimerof diamondoids 1206. The two dimers 1205, 1206 may be coupled to form atetramer of diamondoids 1207, which may comprise an n or p-type deviceat the molecular level. It is contemplated that structures such as thepolymerized diamondoids 1207 may crystallize to form an electricallyconducting molecular crystal.

Optical Devices Fabricated from Diamondoids

The optical materials that may be fabricated according to embodiments ofthe present invention are contemplated to belong to one of twoclasses; 1) passive devices that include lenses, pressure windows,optical waveguides, and antireflection coatings; and 2) active or lightemitting devices, which may have electrical components, including lasersand light emitting diodes, and other optoelectronic devices such asphotoresistors, photodetectors, photodiodes, phototransistors,photovoltaic cells and solar cells. Particle and radiation detectors arealso contemplated.

Lasing in Diamondoid-Containing Materials

The diamondoid-containing laser devices of the present invention arecontemplated to operate by principles delineated below. The interactionbetween radiation and matter as it pertains to lasing has been reviewedby O. S. Heavens et al. in Insight into Optics (Wiley, New York, 1991),chapters 12 and 20, and by E. Hecht in Optics, 2^(nd) Ed.(Addison-Wesley, Reading, Mass., 1990), pp. 577-593. A collection ofatoms may have two energy levels, E₁ and E₂, where the number of atomsin the lower energy state E₁ is n₁, and the number of atoms in thehigher energy state E₂ is n₂. The collection of atoms may exist in aradiation field of frequency c, and a certain number of atoms may absorbenergy from the field such that they are excited from level E₁ to E₂. Anexcited atom in level E₂ may spontaneously decay back to energy levelE₁, thereby giving up a photon in the process having an energy equal tothe difference between E₂ and E₁; this process is spontaneous in that noexternal radiation field is necessary to cause the decay to occur.

In contrast, the excited atom may interact with the radiation field,causing the excited atom to decay to the lower state in a process knownas stimulated emission. Einstein postulated in 1917 that a photonproduced by stimulated emission has three distinct properties: a) it hasthe same phase as the electromagnetic radiation which triggered theexcited atom into stimulated emission; b) it has the same polarizationas the electromagnetic radiation causing the stimulated emission, and c)it propagates in the same direction as the electromagnetic radiationcausing the stimulated emission. Thus, laser light has these threeproperties.

The conditions for light amplication have also been reviewed by O. S.Heavens et al. (1991) and E. Hecht (1990). When the number of stimulatedemissions per second exceed the number of absorptions per second; inother words, when n₂ is greater than n₁, a condition known as populationinversion is achieved. Under this condition an incident photon of theproper frequency triggers an avalanche of stimulated photons, whereinall of the stimulated photons have the same phase. As such, the lightintensity from the emitted photons adds to the intensity of the incidentlight wave, increasing its flux density). As more and more stimulatedphotons are added to the overall flux, the emitted light wave continuesto build as long as there are no competing processes such as scattering,and as long as the population inversion condition is maintained.

Energy must be added to the system to maintain the condition ofpopulation inversion. This process is known as “pumping.” The energypump may be in the form of electrical, chemical, or optical energy.Electrical energy is added to the system in the form of electroniccollisions, and is known as “electron collision excitation.Alternatively, atoms may be elevated in energy to excited states via achemical reaction. Optically, the atoms of a medium may be energeticallyexcited as a result of an absorption of radiation.

Lasers based on doped crystal systems have been reviewed by O. S.Heavens et al. (1991) and E. Hecht (1990). Crystals containing traces oftransition elements, lanthanides, and actinides show broad absorptionbands in certain spectral regions, and sharp fluorescent emissions atlonger wavelengths. One example is the ruby pulsed laser, which utilizesa crystal rod comprising 0.05 percent by weight Cr₂O₃ in Al₂O₃ as theactive medium. To construct a ruby laser, the end faces of the crystalrod are polished, into a flat, parallel, and reflecting configuration inorder to form a resonant cavity. To provide the energy input to maintainpopulation inversion, in this an optical pump, the rod is surrounded bya helical gaseous discharge flashtube. The flashtube provides broadbandoptical pumping to excite Cr³⁺ ions into absorption bands. The excitedCr³⁺ ions rapidly relax (the transition takes about 100 ns) in anon-radiative transition to a pair of metastable states, where the ionsremain for as long as several milliseconds (about 3 ms at roomtemperature).

Because the metastable states have longer lifetimes than the timerequired for the non-radiative transition to take place, a populationinversion may be maintained. The process is initiated when a fewspontaneously emitted photons stimulate a chain reaction. Thereafterexcited atoms in the metastable states are stimulated to decay to theground state, resulting in an in-phase addition of energy to theevolving light wave. Because the ends of the active medium are flat andpolished, the growing light wave can sweep back and forth across theactive medium provided enough sufficient energy is provided to overcomelosses at the mirrored ends. See O. S. Heavens et al. (1991) and E.Hecht (1990).

It is the existence of the broad absorption bands of the active orlasing medium that make the initial excitation possible, and the longlifetime of the metastable states facilitates the condition ofpopulation inversion. A critical component of a laser of this type isthe correct dimensioning of the optical resonant cavity. A device suchas the ruby laser is known as a “three-level laser,” because of thethree energy levels (the absorption bands, the metastable states, andthe ground state) available to the system.

In contrast, a He—Ne laser is a four energy level system because thelower energy level (to which the stimulated photons decay) is not theground state. The four energy level system has advantages in terms ofcontinuous wave operation, as opposed to the three level systems thattypically operate in a pulsed mode.

Other examples of lasing media are the trivalent rare earths Nd³⁺, Ho³⁺,Gd³⁺, Tm³⁺, Er³⁺, Pr³⁺, and Eu³⁺ in a variety of hosts, including CaWO₄,Y₂O₃, SrMoO₄, LaF₃, yttrium aluminum garnet (YAG), and glass.

The mode of achieving the necessary population inversion in asemiconductor laser is different than that used in a doped crystalsystem, as discussed by O. S. Heavens et al. in Insight into Optics(Wiley, New York, 1991), section 20.10.5, pp. 252-253. A semiconductorlaser consists of a p-n junction, which in the absence of an appliedvoltage (also called a bias), demonstrates no light emission. When aforward bias is applied to the p-n junction, however, electrons flowfrom the n-type material into the p-type material to occupy theconduction band of the material in the immediate vicinity of thejunction. A condition of population inversion is established in asemiconductor laser by virtue of a higher concentration of electronsoccupying states in the conduction band of this junction material thanthe concentration of holes occupying states in the valence band.

Whether occurring in a dye laser or in a semiconductor laser, though,population inversion still leads to the same result: spontaneousemission as a result of electrons combining with holes. One differencebetween a dye laser and a semiconductor laser is that with the lattertype of device no external mirrors are required; however, it is stillnecessary for the light emitted from a semiconductor laser to beretained within a resonant cavity. Lasing material that are cubiccrystals with a high refractive index are typically desired forsemiconductor lasers. See O. S. Heavens et al. (1991).

Lasing in Silicon

There appear to be advantages offered by type IV semiconducting opticaldevices; either silicon optical devices for use in silicon-basedmicroelectronic circuitry, or carbon-based optical devices for use indiamond-based technologies. The problem inherent with this approach isthat it is difficult to achieve light emission from a type IVsemiconductor, although nano-sized structures made from type IVsemiconductors appear to offer a solution. In this section, recentsuccess with light emission from silicon will be discussed, followed bya disclosure of the lasing that is contemplated to be possible in adiamondoid-containing materials.

In an article entitled “Optical gain in silicon nanocrystals,” by L.Pavesi et al., Nature, Vol. 408, pp. 440-444, (23 Nov., 2000), thedifficulty of adding optical components to silicon integrated circuitsis discussed. This is because silicon is an indirect-bandgapsemiconductor, and is therefore an inefficient emitter of light. Forthis reason, integration of optically active elements into siliconmicroelectronic circuitry has been achieved largely through the use ofdirect bandgap compound semiconductors. The key component in anoptoelectronic device is a light source, the most desired type being alaser.

Lasing has been observed in type III-V and II-VI direct bandgapsemiconductors, such as gallium arsenide and indium phosphide,respectively, but, to the inventors' knowledge, not in type IV indirectsemiconductors such as silicon. This is because the electron transitionin a direct bandgap semiconductor, with subsequent photon emission,takes place at virtually the same position in momentum (or wave vectork) space, and thus it is not necessary for the transition to be mediatedby a photon. In contrast, an indirect bandgap semiconductor requires thetransition to be mediated by a phonon since a change in k-space takesplace.

These concepts are illustrated in FIG. 13A-B. Referring to FIG. 13A, agraph of electronic energy 1301 is plotted against momentum or wavevector k 1302. The conduction band 1303 is separated from the valenceband 1304 by a bandgap 1305. The bandgap 1305 represents the differencein electron energy between the minimum of the conduction band 1306 and amaximum of the valence band 1307. Electrons may be thermally excitedfrom electronic states at the top of the valence band 1304 to electronicstates at the bottom of the conduction band 1303. Filled states in thediagram are represented by the shaded symbol 1308. It will be noted bythose skilled in the art that electrons thermally excited across thebandgap that fill states in the conduction band 1303 will leave behindholes in the valence band 1304. One such thermal excitation is shown bythe electron 1309, which has created (or left behind) hole 1310.

The direct bandgap semiconductor represented in FIG. 13A displays aminimum in the conduction band 1306 which lies in a substantiallyvertical position above the maximum in the valence band 1307. In otherwords, each of the states (the electron state 1309 and the hole state1310) lie at substantially the same position 1311 in momentum ork-space. Thus, when the electron 1309 decays to fill hole position 1310,emitting a photon 1312, there is essentially no change in the overallmomentum of the system.

This situation is to be contrasted with the indirect bandgapsemiconductor of FIG. 13B. In this case, the minimum 1329 of theconduction band 1323 does not lie in a substantially vertical positionabove the maximum of the valence band 1324, and thus, a change inmomentum of the system equal to about 1350 is required for an electronictransition to occur. For the electron 1329 to decay to fill hole 1330,emitting photon 1332 in the process, a phonon (not shown) having amomentum equal to about the value 1350 mediates the transition. Phononsbasically lead to heat dissipation in the system. This is the reasonthat indirect bandgap semiconductors, such as silicon, are relativelyinefficient emitters of light (L. Pavesi et al, 2000).

Direct bandgap materials (group III-V semiconductors in particular) aslaser sources operate efficiently because electrons and holes recombinedirectly where no phonon is needed to mediate the recombination process;this is a so-called Δk=0 transition (U.S. Pat. No. 6,151,347). TypeIII-V and II-VI are direct bandgap semiconductors lasers, and thereforerequire no phonon mediation, but direct bandgap semiconductors aredifficult to integrate onto silicon-based microelectronic devices. Whatis needed is a silicon laser (L. Canham, 2000). Type IV materials do notradiate light by direct hole-electron recombination, and require aphonon-mediated process to conserve momentum; even so, the longerlifetimes of the phonon-mediated transitional states result in a lowerprobability of radiative emission (U.S. Pat. No. 6,151,347).

Attempts to achieve optical gain in silicon have been discussed in anarticle entitled “Gaining light from silicon,” Nature, Vol. 408, pp.411-428, (23 Nov., 2000). In this article, L. Canham discusses the factthat bulk silicon is an extremely inefficient light emitter, and thus,to make lasers and high-speed telecommunications devices, compoundsemiconductors such as gallium arsenide and indium phosphide are used.These compound semiconductors are, however, difficult to integrate intosilicon integrated circuits.

The manner in which radiative efficiency may be increased, providing thebasis for achieving stimulated emission in indirect bandgapsemiconductors is illustrated in FIG. 13C. The energy dispersionrelationship shown in FIG. 13C shows a minimum in a conduction band 1340that is non-aligned with a maximum in a valence band 1341. Thedescription of an indirect bandgap semiconductor having such non-alignedextreme in k-space is derived from Bloch theory, with the tacitassumption of an infinite lattice; that is to say, a bulk material. Whencharge carriers are restricted in their ability to diffuse randomlythroughout the material, such as materials having a nano ormicrostructure described below, Bloch treatment does not apply becausetrapping or localization of charge carriers in sufficiently small cellsoccurs. Consequently, the solid lines representing the conduction band1342 and the valence band 1343 in FIG. 13C in the E vs. k energydispersion relationship (the electron energy or band energy as afunction of carrier momentum k), are broadened considerably. Thebroadened conduction and valence bands are represented by referencenumerals 1344 and 1345, respectively. Thus, a phonon is not necessary tomediate the transition which may occur between the electron state 1346and hole state 1347, and radiative efficiency in this indirect bandgapsemiconductor is enhanced.

Optical gain has been observed in silicon, and a silicon-based laserdiode may not be long away, according to L. Pavesi. There are apparentlya number of morphologies that may manifest the band broadening describedabove such that electronic transitions may take place without phononmediation. These structures include porous silicon, siliconnanocrystals, silicon/insulator superlattices, and silicon nano-pillars(L. Pavesi, 2000).

The reason a nanostructured or quantum level physical morphology leadsto band broadening appears to lie in the quantum confinement of excitons(an exiton is a bound electron-hole pair) in the nanometer scalecrystalline structures. Evidence for this is a disclosure of a radiativestate associated with a silicon nanocrystal and silicon oxide interface.The silicon nanocrystal comprised about 500 silicon atoms, of whichabout 35 percent were surface atoms). A further approach was thefabrication of silicon-germanium alloys, particularly into quantum wellstructures (U.S. Pat. No. 6,151,347).

Disadvantages of prior art attempts to build optical devices (includinglasers) from semiconductor nanocrystals include lack of uniformity insize and in the size distribution of the nanocrystals. In one examplethis was particularly true in view of the etching techniques used toproduce the nanocrystals (L. Canham, 2002). The diamondoids that are apart of the diamondoid-containing materials of the present areparticularly adept at solving this problem, since each diamondoid,heterodiamondoid, and derivatized diamondoid is a specific molecule witha definitive structure.

Returning now to the problem of developing a silicon laser, L. Pavesi etal. teach the manner in which a silicon microstructure may bemanipulated in order to improve the light emitting properties of thematerial. As previously mentioned, a large number different types ofstructures have been evaluated, each having in common a nanostructuremorphology, or structure that is conducive to quantum level operation.For silicon, these structures have included porous silicon, siliconnanocrystals, silicon/insulator superlattices, and silicon nano-pillars.

According to L. Pavesi et al., the physical principles that lead toincreased photoluminescence in each of these types of siliconmorphologies is essentially that of quantum confinement of exitons in ananometer scale crystalline structure. In some cases, asilicon/dielectric layer (such as silicon dioxide) interface may play arole in passivating radiative states, and forming radiative states.These authors state that although such morphologies are promising withregard to a future role for silicon in photonic applications, a siliconlaser remains unlikely.

As previously alluded to, the production of a silicon laser requires alight amplification process through stimulated emission. However, lightamplification in silicon is difficult to achieve because silicon has anefficient free carrier absorption, which reduces the net gain availablefor lasing, and because there is a significant size dependence on theradiative energies in silicon nanostructures, which causes significantoptical losses in the system.

In keeping with the use of nanostructured materials, and materialscapable of operating at a quantum level, L. Pavesi et al. were able toshow that radiative emission in silicon nanocrystals occurred through aradiative state associated with an silicon/oxide interface. A threelevel model was proposed to explain the observed gain, and the manner inwhich population inversion could be achieved. Two of the proposed levelswere the lowest unoccupied molecular orbital (LUMO) and the highestoccupied molecular orbital (HOMO), which corresponded to the bottom ofthe conduction band and the top of the valance band of the nanocrystal,respectively. In this model, the third level was created by a radiativeinterface state that appears to be responsible for luminescence at 800nm. Electrons were excited such that they populated the higher energylevel LUMO; they then relaxed very rapidly to the interface state thatwas located intermediate in energy between the LUMO and the HOMO.Electrons that populate the interface state have long lifetimes. Becausethe rate of depopulation of the LUMO is much faster than its fillingrate via carrier recommendation mediated by the interface state,population inversion between the interface state and the HOMO could beachieved.

In L. Pavesi et al.'s study, the silicon nanocrystals that displayedoptical gain were thought to contain about 500 atoms, of which about 35percent were surface atoms. Thus, about 150 interface states wereavailable per silicon nanocrystal, with the assumption that each surfacesilicon atom was bound to an oxygen atom of the oxide layer.

Solid State Dye Lasers

A tunable laser is one in which the frequency of the lasing light isadjustable. One type of tunable laser is known as the dye laser becauseit employs an organic dye in solution as the lasing medium. The dye isoptically pumped using a flashlamp or another laser. Laser action occursthrough the emission of light by the excited dye molecules. By employingmultiple dye solutions, dye lasers can be tuned over a wide range ofwavelengths including the ultraviolet, visible, and infrared spectrum.

However, dye lasers that are not solid state possess severaldisadvantages which limits their usefulness and applications requiringportability and long life. For example, a dye laser system requires ameans for providing a continuous flow of the dye solution. Thisnecessitates a substantial amount of expensive and bulky hardware,including pumps, tanks, valves, and other fluid control apparatus.Another requirement of the dye laser is that the temperature of the dyesolution must be maintained within a narrow range close to roomtemperature. Thus, it is necessary to cool the dye solution. Yet anotherlimiting characteristic of the dye laser is that the dye is must bereplaced very frequently due to photochemical association, which maytake place after exposure to ambient light, optical bleaching, andthermal degradation. Dye replacement is often required on a daily basis.

Solid State Diamondoid-Containing Laser Materials Based on NitrogenColor Centers

One type of solid state laser is the color center laser. This type oflaser employs a host material within which are processed a number ofcolor centers that provide the lasing action. Solid-state lasers havingcolor centers as the active lasing material have been discussed in U.S.Pat. No. 4,638,484 to Rand et al., U.S. Pat. No. 4,949,347 to Satoh etal., U.S. Pat. No. 4,950,657 to Nakashima et al., U.S. Pat. No.5,420,879 to Kawarada et al, and U.S. Pat. No. 4,950,625 to Nakashima etal. Such color centers are typically based on defects comprisingnitrogen impurities and their association with lattice vacancies.

Nitrogen aggregates in diamond have been discussed by I. Kiflawi et al.in “Theory of aggregation of nitrogen in diamond,” Properties, Growthand Applications of Diamond, edited by M. H. Nazaré and A. J. Neves(Inspec, London, 2001), pp. 130-133. These authors teach that nitrogenis the major impurity in both natural and synthetic diamond. It is foundboth in dispersed form and aggregated form. A flowchart showing therelationship amongst the different types of diamond, based on the stateof nitrogen aggregation, is given in FIG. 14A. In the actual nitrogenaggregation sequence, nitrogen is incorporated into the diamond latticeas a single substitution on a diamond lattice site. As the nitrogenaggregation sequence continues, other nitrogen-containing centers areproduced that are associated with greater numbers of vacancies. Suchcenters include the H3 center, the N3 center, and the B-center. Innature, nitrogen aggregates (and their associations with vacancies) areformed as a result of a process that takes place over geologic timescales at temperatures which prevailed within the earth's upper mantle.This view is supported by a laboratory experiments in which diamondsannealed at high temperatures displayed the same aggregates.

Nitrogen-vacancy associations have also been discussed by R. Jones etal. in “Theory of aggregation of nitrogen in diamond” in Properties,Growth and Applications of Diamond, edited by M. H. Nazaré and A. J.Neves (Inspec, London, 2001), pp. 127-129. This paper reviewedproperties including the energies and lifetimes of optical transitions,local vibrational modes and vibrational resonances to study thestructure of such color centers. Various types of aggregated nitrogen,and nitrogen vacancy complexes are illustrated in FIG. 14B. Anassociation between a single nitrogen atom and a single lattice vacancyis designated a VN₁ center, also called an H2 center. Those skilled inthe art will note that the nitrogen impurity atom has substitutionallyreplaced one of the four carbons in a tetrahedrally coordinated aroundthe vacancy. In the VN₂ center, also termed an H3 center, a singlelattice vacancy has tetrahedrally coordinated around it two nitrogenatoms substitutionally positioned on diamond lattice sites. The VN₃center, also known as an N3 center, consists of three nitrogen atomstetrahedrally positioned around a single vacancy. In the VN₄ center, orB-center, all four tetrahedral positions surrounding a single vacancyare occupied with nitrogen atoms.

A solid state laser employing a diamond having H3 and N3 color centersas the lasing medium has been discussed by Rand et al. in U.S. Pat. No.4,638,484. Rand disclosed the demonstration of laser action in naturalType I diamonds containing H3 and N3 color centers when excited by anoptical pumping source comprising a light source emitting ultravioletradiation in the 300-600 nm range. High concentrations of N3 colorcenters emitted a bright blue fluorescence, while high concentrations ofH3 centers emitted a bright green-yellow fluorescence. The diamondssuitable for use as laser active materials contained nitrogensubstitutions at a level of at least 0.1 atomic percent. The gaincoefficient of the H3 centers was calculated as 0.09 cm⁻¹, while thegain coefficient for the N3 centers was estimated at about 0.009 cm⁻¹.

A diamond laser comprising a lasing medium having H2 centers has beendescribed by Satoh et al. in U.S. Pat. No. 4,949,347. Laser action waseffected in the range 1000 to 1400 nm by an external light pumpingsource operating at 650 to 950 nm. One method for providing the lasingmedium material comprised the steps of subjecting a synthetic type Ibdiamond having a nitrogen concentration within the range of 1×10¹⁷ to8.5×10¹⁹ atoms/cm³, irradiating the nitrogen-containing diamond with anelectron dose of not less than 5×10¹⁷ electrons/cm², followed by a heattreating step. The heat treating method was optionally performed underultra high-pressure of not less than 3.0 GPa, and high-temperatureconditions of not less than 1500° C. The diamond laser was activatedusing a semiconductor laser(s) as the source of external pumping. Forlaser action using H2 centers, it was necessary to maintain the maximumvalue of the optical density of the H2 centers between 0.01 and 4, whereoptical density is defined as the natural log of the ratio of theincident light intensity to the transmitted light intensity. When thepumping wavelength of Satoh et al.'s diamond laser was varied between500-1000 nm, laser action was observed in the range 1000 to 1400 nm.

A method of preparing a diamond laser crystal with a large quantity ofH3 centers in synthetic Type Ib (single substitutional N) diamond hasbeen disclosed by Nakashima et al. in U.S. Pat. No. 4,950,625. Thismethod involved first preparing synthetic Type 1 b containing at least60 percent of a (111) growth plane, and then thermally treating thatmaterial under high temperature/high pressure conditions such that thetype Ib diamond was converted to type IaA (pairs of N atoms; see FIG.14A). The type IaA diamond was then exposed to an electron beam in orderto generate vacancies. Finally, an annealing step was performed to formH3 centers by coupling the type IaA nitrogen atoms with the vacancies.The number of VN₁ centers was low, which was found to be desirable, asthese are normally an obstacle to laser action.

These methods of producing lasing media with color centers may becumbersome and expensive to implement, and it may difficult to controlthe type, number, and distribution of color centers. What is needed is aset of color center configuration, and methods of manufacturing thesame, wherein control over the type, number, quality, uniformity, anddistribution is readily achievable.

According to embodiments of the present invention, a lasing medium maybe fabricated by allowing diamondoids, nitrogen heteroatom diamondoids,derivatized diamondoids, and derivatized heterodiamondoids tocrystallize into a molecular solid. It is contemplated that the nitrogenheteroatoms may be positioned in the solid adjacent to pores and orvacancies such that a nitrogen-vacancy association is formed, whereinthe number of nitrogens and the number of vacancies in the color centerassembly may be engineered according to the particular structuredesired. This of course determines the properties of the light emitted.In one embodiment of the present invention, an H3 or N3 structure isapproximated. Such a lasing medium is depicted in FIGS. 15A and 15B,where a molecular crystal held together substantially by van der Waalsforces is depicted in FIG. 15A, and a covalently bonded diamondoidpolymer is depicted in FIG. 15B.

Referring to FIG. 15A, a diamondoid-containing material suitable for usein a dye laser having nitrogen-vacancy color centers is depictedgenerally at 1501. Individual diamondoids 1502, 1503, and 1504 pack withindividual heterodiamondoids 1505, 1506, and 1507 forming a pore 1508generally at the center of the group. Heterodiamondoids 1505, 1506, and1507 pack, assemble, or are otherwise constructed such that theirnitrogen heteroatoms are generally positioned adjacent to pore orvacancy 1508 forming a structure that resembles an N3 color center 1509.It will be understood by those skilled in the art that many possiblecombinations of pore sizes, types of heteroatom bonding within eachheterodiamondoid, valence structure of each heteroatom within theheterodiamondoid, geometrical positioning and configuration ofdiamondoids and heterodiamondoids to one another, packing density ofdiamondoids, etc., are possible. Thus, it is possible to control theoptical properties of the color center 1509 within the molecular crystal1501 to achieve the desired laser light properties.

Referring to FIG. 15B, a diamondoid containing material shown generallyat 1510 comprises heterodiamondoids 1511, 1512, and 1513, and diamondoid1514. Heterodiamondoids 1511, 1512, and 1513, contained nitrogenheteroatoms. These four diamondoids may be held in a covalently bondedstructure according to the techniques described for the polymer in FIG.12. The polymerization synthesis is carried out such that the nitrogenheteroatoms of the heterodiamondoids 1511, 1512, and 1513, respectively,are positioned adjacent to a pore, opening, or vacancy 1515. Thenitrogen heteroatoms and pore 1515 form a color center 1516 locatedsubstantially at the center (in this example) of the covalently bondedstructure. The pore does not have to be at the center of the structure.It will be understood by those skilled in the art that many combinationsof covalent bonding structure, choice of heterodiamondoids, degree ofsp² vs. Sp³ character in the covalent bonding, etc., are possible. Thus,it is possible to control the optical properties in the color center1516 within the polymerized material 1510.

An exemplary solid state dye laser that may be constructed to utilizethe lasing medium discussed with regard to FIGS. 15A, B is shown in FIG.16. The dye laser shown generally at 1600 comprises a lasing medium 1601optically pumped by external radiation source 1602, which may be in theform of an array. The external pumping source 1602 emits radiation 1603that excites the color centers (not shown) of the lasing medium 1601.Stimulated emission from the lasing medium 1601 forms coherent laserlight 1604. A lasing medium 1601 is housed with an optical resonator1605. The ends of the lasing medium 1601 comprise a polished andpartially reflecting surface 1606 and a polished and translucent surface1607. The wavelength of the laser light emitted by the die laser 1600may be selected by adjusting a grading 1608. The laser light 1604 may beimpinged on a measuring device or end-use system 1609, or otherwiseprocessed or used.

Advantages of the present molecular crystals and polymerized diamondoidsare that the nitrogen-vacancy containing color center are constructed“from the bottom up,” meaning that the nitrogen heteroatoms and thevacancies comprising the color centers are placed in position by virtueof the details of the assembling technique, whether, crystallization orpolymerization. This may be contrasted with the damaging techniques ofthe prior art methods, wherein nitrogen atoms are either already presentin the crystal, and there is less control over their density ordistribution, or inserted by lattice damaging implantation techniques.Vacancy insertion by ion beam exposure is also more likely to damage acrystal than the synthesis and assembly techniques of the presentembodiments.

The present embodiments include a solid state dye laser which maycomprise a diamondoid-containing lasing medium, an optical pumpingsystem for delivering energy to the lasing medium, and an opticalresonator for processing the light emitted from the lasing medium. Thelasing medium may comprise a diamondoid-containing host material and atleast one color center within the host material. The color center maycomprise at least one nitrogen heteroatom in a heterodiamondoid, wherethe heterodiamondoid may be positioned adjacent to at least one vacancyor pore.

The solid state dye laser may comprise a diamondoid-containing hostmaterial selected from the group consisting of a CVD-deposited film, amolecular crystal, and a polymerized material. The host material maycomprise at least one diamondoid selected from the group consisting ofadamantane, diamantane, and triamantane, and heterodiamondoidderivatives thereof. It may also comprise at least one diamondoidselected from the group consisting of tetramantane, pentamantane,hexamantane, heptamantane, octamantane, nonamantane, decamantane, andundecamantane, and heterodiamondoid derivatives thereof.

Doped Crystal Diamondoid-Containing Laser Medium

A solid state dye laser may also be fabricated according to embodimentsof the present invention by incorporating an optically active dopantwhich is found to lase in the solid matrix.

It is contemplated in the present invention to provide a solid statelaser having as the lasing medium a diamondoid-containing material thatincludes an optically active dopant material that lases within thediamondoid-containing material. Such a device is similar to thatdisclosed in U.S. Pat. No. 5,504,767, except that thediamondoid-containing material of the present disclosure offers the sameabove-mentioned advantages over the diamond of U.S. Pat. No. 5,504,767.

The dopant may be a rare earth element, transition element, actinide, orlanthanide. The dopant may be selected from the group consisting oftitanium, vanadium, chromium, iron, cobalt, nickel, zinc, zirconium,niobium, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium,platinum, gold, mercury, cerium, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium, ytterbium, and uranium. The laser medium is formed as dopantsare included in the diamondoid-containing material as discussed above,wherein the diamondoid-containing material may include a polymericmaterial, ceramic, CVD-nucleated material, molecular crystal, andcombinations thereof.

The elements of a diamond laser have been discussed by Jamison et al. inU.S. Pat. No. 5,504,767. According to Jamison et al., a laser containsthree elements; 1) a lasing medium, which generates the laser light, 2)a power supply, which delivers energy to the laser medium in a form aneeded to excite it to emit light, and 3) and optical cavity orresonator which concentrates light to simulate the emission of laserradiation.

In one type of solid state laser, the laser medium comprises acrystalline solid host, which is doped with the species that emits thelaser light. The active species is embedded in the host. The activespecies is excited to lase, or is pumped, by light from external source.A variety of crystals and glasses have been used as hosts in the mediumof a solid state laser. The main requirements of the host aretransparency, ease of fabrication, and good heat transfercharacteristics.

Also discussed by Jamison et al. in U.S. Pat. No. 5,504,767 are theadvantages that diamond displays as a potential host for lasing ions toform a solid state laser. These advantages are due to the extremely highthermal conductivity and large bandgap of diamond. Diamond is about 200times more resistant to thermal shock in a high power optical systemsthan any other me of material, and therefore may provide the basis forproducing extremely high power density solid state laser. The highthermal conductivity of diamond will also minimize thermal lensing,caused by a change in the refractive index of the hostdiamondoid-containing material as its temperature increases duringoperation. This is contemplated to allow a diamondoid based laser tooperate at a higher power density than a conventional solid state laser.

Another advantage a diamondoid based laser offers stems from the verywide bandgap that a diamondoid-containing material is expected to have.A diamondoid based material is expected to have a bandgap higher thanabout 3 eV (in some embodiments greater than about 4 eV, and in stillother embodiments greater than about 5 eV), such that higher energyphotons pass of through the crystal than otherwise would have occurredwith a traditional solid state laser host material.

Optically active dopants are inserted into a diamondoid-containingmaterial according to present embodiments by self-assembly,crystallization, and polymerization techniques similar to those used fornitrogen-vacancy color centers. An exemplary self-assembled orcrystallized material suitable for use in a solid state laser is showngenerally at 1700 in FIG. 17A. Diamondoids 1702-1707 may be generallydisposed around an optically active dopant 1708. The optically activedopant 1708 may comprise a rare earth element, transition element,actinide, or lanthanide, or mixtures thereof. The optically activedopant may be selected from the group consisting of titanium, vanadium,chromium, iron, cobalt, nickel, zinc, zirconium, niobium, cadmium,hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold,mercury, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, and uranium. Some of the diamondoids surrounding theoptically active dopant 1708, and comprising the pocket in which thedopant sits, may be either positioned in close proximity to the dopantatom, in contact with it, or even bonded to it in some manner, such asthrough a covalent or ionic bond, or through London forces. Exemplarydiamondoids in FIG. 17A include 1703, 1705, and 1707. Other diamondoidscomprising the pocket may be positioned further away from the dopantatom; such diamondoids include 1702, 1704, and 1706. These more distantdiamondoids may also exert a force on the dopant, or no force at all.The dopant atom may also be chemically inert with respect to itsdiamondoid hosts. Of course, in keeping with the definition ofdiamondoids in this disclosure, the diamondoids may also beheterodiamondoids, or derivatives thereof.

A polymerized diamondoid-containing material that may host an opticallyactive dopant atom is shown generally at 1710 in FIG. 17B. Thisexemplary material comprises four diamondoids 1711-1714 that form a porewithin which an optically active dopant atom 1715 resides. As with themolecular crystal 1701, any of the diamondoids 1711-1714 that comprisepolymerized material 1710 may contact or be bonded in some manner to thedopant atom, or they may be chemically inert to it and the opticallyactive dopant atom 1715 may be held in place mechanically.

The diamondoid-containing materials of FIGS. 17A, B may also be used inthe solid state laser of FIG. 16.

Diamondoid-Containing Semiconducting Lasers and LED's

A light emitting diode constructed from materials of the presentembodiments may be formed by joining an n-type diamondoid-containingmaterial with a p-type material; an n-type material and a p-typediamondoid-containing material, or a p-type diamondoid-containingmaterial and an n-type diamondoid-containing material, to form a p-njunction. The p-n junction is then forward biased, meaning that anegative voltage is applied to the n-type side of the junction, and apositive voltage is applied to the p-type side of the junction. The p-njunction may be forward biased by applying an electric field or anelectric potential across the diode, and in particular, its p-njunction. Forward biasing causes electrons to be excited from the n-typematerial, across the p-n junction, into the p-type material, wherein theelectrons combine with holes. Each time an electron combines with ahole, a photon may be emitted.

Current injection type light emitting devices employing diamond havebeen disclosed by Horiuchi et al. in U.S. Pat. No. 6,433,474. Such acurrent injection type light emitting devices makes use of a diamondmedium to emit ultraviolet light. The device emits ultraviolet radiationas a consequence of free exiton recombination within the diamondmaterial as a result of the application of the DC voltage appliedbetween two electrodes to inject carriers into the diamond.

Horiuchi et al. teach the p-n junction such an ultraviolet lightemitting diamond device can be used in the field of optical informationrecording, readout processing, photolithography, optical working, andflorescent light sources. Since ultraviolet light has a shortwavelength, demands for such a device are numerous due to the highfrequency and therefore high bandwidth provided by ultraviolet light.Horiuchi et al.'s device comprises a luminescent layer where emissionoccurs such that free excitation recombination radiation due toexcitation by the injection of current is dominant. This is possibleonly with high-quality diamond having with few lattice defects exceptfor the dopant atoms that are deliberately inserted.

A “dominant” emission whose origin is a free exiton recombination isdefined by Horiuchi et al. as an emission whose intensity is least twiceas large as an emission arising from impurities. Horiuchi et al.'shigh-quality diamond crystal is fabricated by a high-temperature andhigh-pressure method using a nitrogen getter so that the amount ofnitrogen contained in the crystal is no more than about 10 ppm. Thepresence of nitrogen in the diamond, in addition to lattice defects,adversely affects the free exiton recombination radiation. The preferreddiamond material is p-type semiconductor containing boron, where theboron content is no greater than 40 ppm as measured by infraredspectroscopy, or no more than about 2×10¹⁹ atoms/cm³ as measured bysecondary ion mass spectroscopy (SIMS).

To maximize the wavelength of the objective emission, which in this caseis in the ultraviolet wavelength of the electromagnetic spectrum, thenumber of impurities and defects in the crystal should be minimized.Diamond exhibits a bandgap (Eg) at room temperature of approximately5.47 eV (wavelength 227 nm), and a bound energy of a free exiton (Eb) ofapproximately 80 meV; therefore, the frequency of free exitonrecombination radiation is Eg-Eb, or 5.39 eV (230 nm). However, diamondhas the band structure of an indirect transition type of semiconductor,and thus a variety of phonon mediated events accompany the emission of aphoton. One in particular is an emission associated with one or moretransverse optical phonons whose creation results in an emission with anenergy at room temperature in the vicinity of 5.28 eV (235 nm), 5.12 eV(242 nm), 4.98 eV (249 nm), and 4.82 eV (257 nm). These plural phononside bands overlap to form a luminescence emission band which isobservable. Generally, the accumulated emissions from these phonon sidebands are called “free exiton recombination radiation.”

It is important to stress that such radiation may only be observed forhigh-quality diamond crystals having a minimum of impurities anddefects. Horiuchi et al. achieve such impurity and defect free diamondcrystals using high-temperature and high-pressure method is employing anitrogen getter, and state that such a method is suitable for providingan ultraviolet light emitting diamond crystal, whereas natural diamondand diamond grown by CVD methods are not capable of providing suchdefect and impurity free crystal qualities. However, thehigh-temperature and high-pressure synthesis methods can be difficult tocarry out. In such a method, carbon raw material is dissolved in theflux metal and a temperature pressure regime such that the diamond canstably exist and precipitate on a seed crystal. What is needed aremethods for producing defect and impurity free diamond or diamond likematerials with more reliable and controllable techniques.

The diamondoid-containing materials of the present convention offer sucha solution. It is contemplated that any of the methods disclosed above,including CVD generated diamondoid containing films, self assembled orcrystallized clusters of diamondoids (molecular crystals), orpolymerized diamondoid-containing films are suitable for producingdevices that emit short wavelength radiation. Of particular interest aremolecular crystals of diamondoids containing no heteroatoms, as it hasbeen observed that they hydrogenated diamond surface exhibits p-typeelectrical properties, and a molecular crystal of the diamondoids of thepresent embodiments display a very large surface to volume ratio.

A suitable ultraviolet emitting current injection type device (laser orLED) in which the above-mentioned diamondoid containing materials aresuitable is shown in FIG. 18. Referring to FIG. 18, a current injectiontype ultraviolet light emitting device shown generally at 1800 comprisesa diamondoid-containing material 1801 sandwiched between an electrode1802 and an electrode 1803. The diamondoid-containing material 1801 inone embodiment is a molecular crystal of diamondoids having noheteroatoms such that the hydrogenated surface of the diamondoidsdisplay p-type electrical properties. In this embodiment, the electrodes1802, 1803 may comprise a conducting metal such as silver that may besputtered onto two opposing sides of the diamondoid-containing material1801. The electrodes 1802, 1803 are connected via wiring 1804,1805,respectively to a power supply 1806. The polarity of the power supply1806 and wiring 1804, 1805 is configured such that electrons areinjected from the electrode 1803 into the diamondoid containing material1801, creating holes and free exitons in the diamondoid-containingmaterial 1801. The diamondoid containing material 1801 is of sufficientquality, meaning a low concentration of impurities and defects, suchthat free exitons may combine with one another, and free exitonrecombination radiation can be achieved.

The basis for a semiconductor laser according to embodimentscontemplated by the present inventors is discussed in relation to FIGS.19A-C. A semiconductor laser is shown schematically at 1900 in FIG. 19A,where contacts 1901, 1902 are shown connected to a p-typediamondoid-containing material 1903, and a n-type diamondoid-containingmaterial 1904, respectively. As a forward bias is applied to thejunction region 1905, laser light 1906 is emitted.

The mode of achieving the necessary population inversion in asemiconductor laser is different from the mechanisms that apply to dyelasers. Referring to FIG. 19B, one of skill in the art will recognizethe band structure for a p-n Junction without any bias, and in FIG. 19C,the same p-n junction with a forward bias. As previously explained,electrons flow from the n-type material into the p-type material,occupying the conduction band of the material in the immediate vicinityof the junction. In this region, a higher concentration of electronicstates in the conduction band is occupied relative to that of the holestates in the valence band. Upon making a downward transition 1907between the two states, as shown in FIG. 19C, the system emitsrecombination radiation (not shown) which serves as the spontaneousemission for initiating laser action. For this type of laser, noexternal mirrors are needed.

It is contemplated that the n and p-type diamondoid-containing materialsdiscussed in an earlier section of this disclosure are suitable forforming the p-n junction of a semiconductor laser.

Similar devices that may be fabricated from the n and p-type materialsdisclosed above include photoresistors, photodiodes, solar cells, andphototransistors. Such devices have been discussed in a chapter onOptoelectronics by P. Scherz in “Practical Electronics for Inventors,”(McGraw-Hill, New York, 2000), chapter 5. A photoresistor is a lightcontrol variable resistor. In terms of operation, a photoresistor isusually very resistive when placed in the dark, however; when it iseliminated, its resistance decreases significantly. Potentialapplications of a diamondoid-containing photoresistor include light anddark activated switching circuits and light-sensitive detector circuits.Photodiodes are devices that convert light energy directly into anelectric current. If the anode and cathode leads of the photodiodes arejoined together by a wire and then the photodiodes is placed in thedark, no current will flow. However, when the photodiode is illuminated,it becomes a small current source that pumps current from the cathodethrough the wire into the anode. Applications of photodiodes includedetectors of fast pulses of light used in wireless communications. Solarcells are photodiodes with very large surface areas. The transistors arelight sensitive transistors. A common type of phototransistor resemblesa bipolar transistor with its base lead removed, and replaced with alight-sensitive surface area. When the surface area is kept dark, thedevice is off, and no current flows through the collector to emitterregion. When the light-sensitive region is exposed to light, a smallbase current is generated that controls and much larger collector toemitter current. Field effect photo transistors are light-sensitivefield effect transistors. Unlike bipolar transistors, field effect phototransistors use light to generate a gate voltage that is used to controlin train source current.

According to embodiments of the present invention, a light emittingdiode may comprise comprises a diamondoid-containing material having abandgap, and a means for generating an electric field to cause at leastone electronic transition such that light is emitted from the diode. Theelectronic transition may occur across the bandgap, and further, thelight emitting diode may be configured such that

the electronic transition occurs without participation of electronicstates within the bandgap. The bandgap of the diamondoid-containingmaterial is at least 3 eV in one embodiment, at least 4 eV in anotherembodiment, and at least 5 eV yet another embodiment. The wavelength ofthe emitted light may be in the ultraviolet range of the electromagneticspectrum.

Similarly, a photodetector may comprise a diamondoid-containing materialhaving a bandgap, and a means of processing current from at least oneelectronic transition that results from the absorption of light by thematerial. The electronic transition may occur across the bandgap, andfurther, the light emitting diode may be configured such that theelectronic transition occurs without participation of electronic stateswithin the bandgap. The bandgap of the diamondoid-containing material isat least 3 eV in one embodiment, at least 4 eV in another embodiment,and at least 5 eV yet another embodiment. The wavelength of the emittedlight may be in the ultraviolet range of the electromagnetic spectrum.

Charged Particle Detectors

The diamondoid-containing materials are contemplated to be useful asparticle detectors. Such a device has been described by Lu et al. inU.S. Pat. No. 5,773,830. The solid-state radiation detector described byLu et al. operates by establishing a strong electrical field between twoelectrodes within which is positioned a freestanding insulatingmaterial. When the insulating material is exposed to radiation ofsufficient energy to bring electrons or electron-hole pair carriers intothe conduction band of the insulating material, the carriers are sweptto the electrodes by the electric field. Their arrival can be measuredby an electronic signal detection device connected to the electrodes.

It is recognized that diamond in general is a particularly advantageousmaterial for use in a solid-state particle detector because diamond ismuch more resistant to radiation damage than our alternative detectormaterials such as silicon having a p-n junction. Silicon detectorssuffer crystal structure damage when exposed to high radiation whichleads to an increased leakage current and decreased pulse height andoutput signal. Furthermore, in silicon, the maximum field that can beapplied before avalanche breakdown is about 10³ V/cm. This limits thecharge velocity to approximately 106 cm per second, so that thecollection time is at least 20 ns for a detector having a thickness ofthe few hundred microns.

Lu et al. disclose a method of producing a diamond film via an arcjetCVD deposition process. The material produced demonstrated a collectiondistance of 35 to 50 microns, a mobility of 3000 to 4000 cm² V⁻¹ s⁻¹,and a lifetime of over 1 ns. This lifetime is higher than 8150 picoseconds typically reported for CVD diamond, and higher than 3300 550pico seconds for natural type IIa diamond.

And exemplary particle detector suitable for use according to thepresent embodiments is shown generally at 2000 in FIG. 20A. The devicecomprises a diamondoid-containing material 2001 having two ohmic contactelectrodes 2002, 2003. The electrodes 2002, 2003 are connected to signalprocessing circuitry which includes a voltage source 2004 in series witha load resistor 2005. An amplifier 2006 is connected to the electrodes2002 via an isolation capacitor 2007. In operation, a charged particle2008 passes through the detector 2000 following approximately path 2009,in the process creating an electron hole pair at approximately position2010. The electron diffuses to the positively charged electrode 2002,where the hole diffuses to the negatively charged electrode 2003,creating a signal in the external circuit which is amplified by theamplifier 2006.

An alternative embodiment of the particle or radiation detector is shownin FIG. 20B. In FIG. 20B, the electrodes 2002 and 2003 have beensubdivided such that various portions of the electrodes servicedifferent portions of the diamondoid-containing material 2002.Advantages of this embodiment are that because multiple regions of thediamondoid-containing material 2001 are under the influence of differentpairs of electrodes, damage sustained by one portion of the detectordoes not prevent another part of the detector from being sensitive toparticles or radiation. As shown in FIG. 20B, the pair of electrodes2002B, 2003B energizes the left hand region of the detector, and thepair of electrodes 2002A, 2002B energizes the right hand region of thedetector. Thus, if a particle 2021 damages the left hand region suchthat the region of material 2023 is no longer sensitive to radiation, aparticle 2022 may still be detected by the still operable region 2024.

Anti-Reflection Coatings

It is contemplated that the diamondoid-containing materials of thepresent embodiments will be useful as either one or both of thealternating layers of an antireflection coating. The theory ofantireflection coatings has been discussed by O. S. Heavens and R. W.Ditchburn in Insight into Optics (Wiley, New York, 1991), pp. 44-46.

Exemplary antireflection coatings are shown in FIG. 21A, B. Referring toFIG. 21A, an antireflection coating shown generally at 2100 comprisesalternating layers of high refractive index and low refractive indexmaterials deposited on a substrate 2101. The layers comprisingantireflection coatings 2100 are of equal optical thickness of ¼ ofwavelength of the light impinging on the substrate 2101 such thattransmission twice through any one layer produces a phase difference ofpi.

Operation of the antireflection coating may be discussed more easilywith reference to FIG. 21B, which shows the result of rays impinging ona single element of a quarter wave stack 2110. The single element 2110comprises a single layer of a high refractive index material 2110, and alow refractive index material 2111. Supposing that the phase of anincident wave 2115 on the single element 2110 is 0, then reflected beam2116 one has a phase pi (due to reflection), and reflected beam 2117 hasno face difference due to reflection, but a phase difference of pi dueto transmission twice. Reflected beam 2118 has a phase difference of 2pi due to transmission and pi due to reflection, making 3 pi, so that itis in phase with beams 2116 and 2117. Thus by successive destructiveinterference of each set of two waves, the reflection is zero.

Advantages of a diamondoid-containing layer's 2110 is that due to thelayer's high refractive index, the thickness of the layer may be thin,thereby allowing for a greater number of layers and greater efficiencyin creating a state of destructive interference.

All of the publications, patents and patent applications cited in thisapplication are herein incorporated by reference in their entirety tothe same extent as if the disclosure of each individual publication,patent application or patent was specifically and individually indicatedto be incorporated by reference in its entirety.

Many modifications of the exemplary embodiments of the inventiondisclosed above will readily occur to those skilled in the art.Accordingly, the invention is to be construed as including all structureand methods that fall within the scope of the appended claims.

1. An optical device comprising a diamondoid-containing material,wherein the optical device is selected from the group consisting of aphotoresistor, a phototransistor, a photovoltaic cell, and a solar cell.2. The optical device of claim 1, wherein the diamondoid-containingmaterial comprises at least one higher diamondoid.
 3. The optical deviceof claim 1, wherein the at least one higher diamondoid is a derivatizedhigher diamondoid.
 4. (canceled)
 5. The optical device of claim 1,wherein the diamondoid-containing material is selected from the groupconsisting of a CVD-deposited film, a molecular crystal, and apolymerized material.
 6. The optical device of claim 1, wherein thediamondoid-containing material comprises at least one diamondoidselected from the group consisting of adamantane, diamantane, andtriamantane, and heterodiamondoid derivatives thereof.
 7. The opticaldevice of claim 1, wherein the diamondoid-containing material comprisesat least one diamondoid selected from the group consisting oftetramantane, pentamantane, hexamantane, heptamantane, octamantane,nonamantane, decamantane, and undecamantane, and heterodiamondoidderivatives thereof.
 8. The optical device of claim 1, wherein thediamondoid-containing material comprises at least one heterodiamondoidderivative.
 9. The optical device of claim 6, wherein thediamondoid-containing material comprises at least one heterodiamondoidderivative.
 10. The optical device of claim 7, wherein thediamondoid-containing material comprises at least one heterodiamondoidderivative.